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Jaka Sunarso

Swinburne University of Technology, Sarawak, Faculty of Engineering Computing and Science, Faculty Member

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I am an experienced electrochemist endowed with 5 years of Master and Ph.D. working experience in proton conducting membrane and mixed ionic-electronic conducting membrane and cathode materials as well as 4 plus years of postdoctoral working experience in battery materials. My interest therefore lies in these related electromaterials area which are of substantial value to provide sustainable society where energy forms an important part of it.

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Catholic University of Korea

Reidar Haugsrud

Wilhelm Meulenberg

Griffith University

Norwegian University of Science and Technology

Chungnam National University

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Papers by Jaka Sunarso

Perovskite-based proton conducting membranes for hydrogen separation: A review

Hydrogen is considered a fuel of the future due to its diversified supply and zero greenhouse gas... more Hydrogen is considered a fuel of the future due to its diversified supply and zero greenhouse gas emission. The application of advanced membrane technology for hydrogen separation within the larger hydrogen production process context can substitute the use of more expensive and energy intensive cryogenic distillation and pressure swing adsorption technologies. This review overviews the basic aspects and progresses in perovskite-based proton conducting hydrogen separation membranes. Different configurations such as symmetric, asymmetric, hollow fiber, and surface modified perovskite membranes with various compositions are discussed and summarized. The challenges and future directions of such membranes are also elaborated.

CO2 erosion of BaCo0.85Bi0.05Zr0.1O3-δ perovskite membranes under oxygen permeating conditions

CO2-resistant oxygen selective ceramic membranes have wide applications in clean energy delivery ... more CO2-resistant oxygen selective ceramic membranes have wide applications in clean energy delivery and green chemical synthesis. In this work, CO2 erosion and O2 permeation behavior of BaCo0.85Bi0.05Zr0.1O3-δ (BCBZ) perovskite hollow fibre membranes are investigated. The BCBZ hollow fibre was fabricated by a combined phase-inversion and sintering technique. Experimental results indicate that the O2 permeation flux can reach 3.07 mL cm−2 min−1 at 1000 °C under the air/Ar gradient whereas the O2 flux reduced significantly in CO2 presence depending on the CO2 concentration in the feed gas or sweep gas. The deteriorating effect of CO2 on the membrane performance in the feed side was more significant than when it was present in the permeate side. One of the BCBZ hollow fibre samples had been tested for more than 190 h; undergoing six thermal cycles from 700 to 1000 °C in different CO2-containing gas streams. With high CO2 concentrations up to 10 vol.% in both feed and permeate sides, no permeation was observed due to the strong CO2 adsorption on the membrane surface; however, the O2 flux can be completely recovered once the CO2 became absent in the gas atmosphere. When the membrane test was continued up to 180 h, the O2 flux value cannot be fully recovered and 9.6% of the original flux value was lost due to the carbonate salt formation. To get the quantitative information on the erosion rate, more membrane samples had been tested from 1 to −8 days in 10 vol.% CO2 at 900 °C under the oxygen permeating conditions. We found that the erosion rate was relatively fast at the beginning stage with corrosion depth up to 3 µm for the first 3 days but slowed down to 1 µm depth for the subsequent 5 days. The significantly reduced erosion rate is due to the higher O2 concentration in the locally uncontaminated membrane area (without the carbonate deposition). Inspired by such findings, one future strategy to protect the membrane is to deposit the membrane surface using more robust ion-conducting layer like Sm0.2Ce0.8O1.9 .

Revamping existing glycol technologies in natural gas dehydration to improve the purity and absorption efficiency: Available methods and recent developments

The glycol purity limit in conventional absorption-based natural gas dehydration process has led ... more The glycol purity limit in conventional absorption-based natural gas dehydration process has led to the significant water vapour presence in the supposedly dry product gas. Several alternative processes have been developed to overcome this limitation that includes stripping gas injection using nitrogen, a portion of dry product gas, or volatile hydrocarbon (DRIZO process), stripping gas modified with Stahl column, and Coldfinger technology. This review summarises these different processes and elaborates on their mechanisms, process flow diagram, advantages, drawbacks, and current statuses. Relevant works from 1991 to 2017 were compiled and the existing gaps were highlighted as recommendation for future work.

Modeling of hydrogen separation through porous YSZ hollow fiber-supported graphene oxide membrane

In this work, hydrogen (H2) permeation fluxes through 230 nm-thick graphene oxide (GO) membrane d... more In this work, hydrogen (H2) permeation fluxes through 230 nm-thick graphene oxide (GO) membrane deposited on porous YSZ hollow fiber were measured and correlated to an explicit H2 permeation model. H2 fluxes through such GO-YSZ hollow fiber membrane increased from 4.83 x 10-8 mol cm-2 s-1 to 2.11 x 10-7 mol cm-2 s-1 with temperature rise from 20 to 100 oC. The activation energy of H2 permeation was determined by the linear regression of the experimental data and was applied in the theoretical calculations. The model predictions fit well the temperature dependent and the argon sweep gas flow rate dependent H2 fluxes data. Using the derived permeation model, the effects of vacuum pressure at lumen side and H2 partial pressure at shell side, membrane area, and GO membrane film thickness on the membrane performance were simulated and discussed to provide insights for practical applications.

Active centers of catalysts for higher alcohol synthesis from syngas: A review

The gradual depletion of oil resources and the necessity to reduce greenhouse gas emissions portr... more The gradual depletion of oil resources and the necessity to reduce greenhouse gas emissions portray a concerning image of our contemporary security of liquid transportation fuels in the event of a global crisis. Despite a vast amount of natural gas resources that we have and the huge economic incentive, the conversion of gas to liquid fuels or chemicals is still very limited because of the high technological complexity and capital cost for facilities. However, with the anticipated depletion of liquid petroleum and the soaring price of crude oil, the conversion of natural gas to liquid feedstock or fuels will become more and more important. Higher alcohols are important feedstocks for the chemical and pharmaceutical industries and have wide applications as potential fuel additives or hydrogen carriers for fuel cells for clean energy delivery. There is a long-standing interest in the synthesis of higher alcohols from syngas, an important Fischer−Tropsch technology for natural gas conversion. The purpose of this review is to provide readers with an extensive account of catalytic synthesis of higher alcohols from syngas using various catalysts reviewed from a unique perspective: clarification of the active centers and reaction pathways. In light of the different sources providing the active centers, three major classes of catalysts in terms of monometallic, bimetallic, and trimetallic/multimetallic catalysts are systematically reviewed, and their respective performances are carefully compared. Finally, future works proposed to improve the catalyst design are described.

New phosphorus-doped perovskite oxide as an oxygen reduction reaction electrocatalyst in an alkaline solution

Because of their structural and compositional flexibility, perovskite oxides represent an attract... more Because of their structural and compositional flexibility, perovskite oxides represent an attractive alternative electrocatalyst class to precious metals for the oxygen reduction reaction(ORR); an important reaction in fuel cells and metal–air batteries. Partial replacement of the original metal cation with another cation ,namely, doping, can be used to tailor the ORR activity of perovskite, for which a metal has been exclusively used as the dopant component in the past. Herein, phosphorus is proposed as a non-metal dopant for the cation site to develop a new perovskite family with the formula of La0.8Sr0.2Mn1-xPxO3-d (x = 0, 0.02, 0.05, and 0.1; denoted as LSM, LSMP0.02, LSMP0.05, and LSMP0.1, respectively). Powder XRD patterns reveal that the solubility of phosphorus in the perovskite structure is around 0 .05. Rotating ring-disk electrode experiments in the form of linear-sweep voltammetry scans demonstrated the best ORR performance for LSMP0.05, and also revealed close to a four-electron ORR pathway for all four compositions. A chronoamperometric test (9000 s) and 500 cycle accelerated durability test demonstrated higher durability for LSMP0.05 relative to that of LSM and the commercial 20 wt %Pt/C catalyst. The higher ORR activity for LSMP0.05 is attributed to the optimised average valence of Mn, as evidenced by combined X-ray photoelectron spectroscopy and soft X-ray absorption spectroscopy data. Doping phosphorus into perovskites is an effective way to develop high-performance electrocatalysts for ORR.

Towards enhanced energy density of graphene-based supercapacitors: Current status, approaches, and future directions

Despite high power density, fast charging/discharging rate, and long operational lifetime, large-... more Despite high power density, fast charging/discharging rate, and long operational lifetime, large-scale application of supercapacitor (SC) is limited by its intrinsically low energy densities (of 5–8 Wh kg−1 (gravimetric) and 5–8 Wh L−1 (volumetric)), which are at least 10-fold lower than battery. Since the invention of graphene in 2004, graphene-based SCs have set the upper performance limit of the symmetric carbon-based SCs due to superior electrical conductivity and very high accessible surface area of graphene. Still, only two companies have commercialised graphene-based supercapacitors thus far. Their maximum achievable energy density (i.e., 11.65 Wh kg−1) is too low to make them competitive against batteries in high-energy applications. To this end, this comprehensive review focuses on the material- and device-level approaches to high energy density graphene-based conventional macroscale SCs (≥11.65 Wh kg−1) and flexible SCs and microsupercapacitors (≈0.3–10 mWh cm−3; ≈300–16000 μWh cm−2). It includes a description on how each approach is implemented and an explanation of how each can provide effective research results. This review also meticulously discusses the underlying challenges and possible solutions to achieve high energy density graphene-based SCs in practice.

Mixed protonic-electronic conducting perovskite oxide as a robust oxygen evolution reaction catalyst

Large-scale utilization of hydro, solar, or wind-based electrochemical water splitting relies on ... more Large-scale utilization of hydro, solar, or wind-based electrochemical water splitting relies on the availability of low cost, highly active oxygen evolution reaction (OER) catalyst. Transition metal-containing perovskite oxide is attractive in this regard. The OER on such perovskite oxide in an alkaline solution is nonetheless often limited by proton transfer step. To overcome such limitation, here we apply mixed protonic-electronic conductor BaCo0.8-xFexZr0.1Y0.1O3 (x = 0, 0.2, and 0.4) as an OER catalyst. Among these three, BaCo0.8Zr0.1Y0.1O3 (BC0.8ZY) in particular shows the lowest OER overpotential, the lowest Tafel slope, the highest OER mass activity, and the highest OER specific activity, which surpass those of Ba0.5Sr0.5Co0.8Fe0.2O3-d (BSCF) benchmark. Using O2-temperature programmed desorption, impedance spectroscopy, and O1s X-ray photoelectron spectroscopy, we attribute such superior OER performance to the highest oxygen desorption capacity, the lowest charge transfer resistance, and the highest hydroxide species content for BC0.8ZY. We also demonstrate that the OER current of BC0.8ZY exhibits a first-reaction order dependence to the solution pH between 12.5 and 14, which confirms its proton transfer rate-determining step.

Chem Eng Res Des_134_2018_487_496.pdf

Hollow fiber Membrane Oxygen permeation a b s t r a c t Oxygen-selective perovskite hollow fiber ... more Hollow fiber Membrane Oxygen permeation a b s t r a c t Oxygen-selective perovskite hollow fiber membrane can be used to obtain an effective oxygen separation from air at high temperature (above 700 • C) for large scale application. Here, we display that oxygen permeation fluxes of La 0.6 Sr 0.4 CoO 3 (LSC 113 ) hollow fiber membrane was enhanced by macrostructure modification and (La,Sr) 2 CoO 4 (LSC 214 ) surface decoration. By changing the cross-section macrostructure from sandwich structure (for LSC-a fiber) to asymmetric structure (for LSC-b fiber), the oxygen flux was improved by up to 3.6-fold.

Carbon and non-carbon support materials for platinum-based catalysts in fuel cells

Carbon and other platinum-supporting materials have been studied as electrode catalyst component ... more Carbon and other platinum-supporting materials have been studied as electrode catalyst component of low-temperature fuel cells. Platinum (Pt) is commonly used as the catalyst due to its high electro-catalytic activity. Current research is now focusing on using either modified carbon-based or non-carbon-based materials as catalyst supports to enhance the catalytic performance of Pt. In recent years, Pt and Pt-alloy catalysts supported on modified carbon-based and non-carbon-based materials have received remarkable interests due to their significant properties that can contribute to the excellent fuel cell performance. Thus, it is timely to review this topic, focusing on various modified carbon-based supports and their advantages, limitations and future prospects. Non-carbon-based support for Pt and Pt-alloy catalysts will also be discussed. Firstly, this review summarises the progress to date in the development of these catalyst support materials; from carbon black to the widely explored catalyst support, graphene. Secondly, a comparison and discussion of each catalyst support in terms of morphology, electro-catalytic activity, structural characteristics , and its fuel cell performance are emphasized. All the catalyst support materials reviewed are considered to be promising, high-potential candidates that may find commercial value as catalyst support materials for fuel cells. Finally, a brief discussion on cost relating Pt based catalyst for mass production is included.

Systematic study of oxygen evolution activity and stability on La1−xSrxFeO3−δ perovskite electrocatalysts in alkaline media

Perovskite oxide is an attractive low-cost alternative catalyst for oxygen evolution reaction (OE... more Perovskite oxide is an attractive low-cost alternative catalyst for oxygen evolution reaction (OER) relative to the precious metal oxide-based electrocatalysts (IrO2 and RuO2). In this work, a series of Sr-doped La-based perovskite oxide catalysts with compositions of La1−xSrxFeO3−δ (x = 0, 0.2, 0.5, 0.8, and 1) are synthesized and characterized. The OER-specific activities in alkaline solution increase in the order of LaFeO3−δ (LF), La0.8Sr 0.2FeO3−δ (LSF-0.2), La0.5Sr0.5FeO3−δ (LSF-0.5), SrFeO3−δ (SF), and La0.2Sr0.8FeO3−δ (LSF-0.8). We establish a direct correlation between the enhancement in the specific activity and the amount of surface oxygen vacancies as well as the surface Fe oxidation states. The improved specific activity for LSF-0.8 is clearly linked to the optimum amount of surface oxygen vacancies and surface Fe oxidation states. We also find that the OER performance stability is a function of the crystal structure and the deviation in the surface La and/or Sr composition(s) from their bulk stoichiometric compositions. The cubic structure and lower deviation, as is the case for LSF-0.8, led to a higher OER performance stability. These surface performance relations provide a promising guideline for constructing efficient water oxidation.

Significantly improving the durability of single-chamber solid oxide fuel cells: A highly active CO2‑resistant perovskite cathode

The single-chamber solid oxide fuel cell (SC-SOFC) represents an attractive alternative to batter... more The single-chamber solid oxide fuel cell (SC-SOFC) represents an attractive alternative to batteries for micropower applications given its simplified stack design, easy gas management, lower operation temperature, and quicker start-up. Its stable operation over long duration relies on the availability of CO2-resistant cathode materials with high oxygen reduction reaction (ORR) activity. Here, we reported a novel perovskite oxide cathode SrSc 0.075 Ta 0.025 Fe 0.9 O 3−δ (SSTF75), which provides CO 2 resistance and high ORR activity. A peak power density of 1430 mW cm −2 was achieved with the SSTF75/Sm0.2Ce0.8O1.9 cathode at 650 °C with a methane and oxygen gas mixture (1:1 v/v ratio). It retained stable voltage performance at 600 °C for an over 90 h duration when discharged at a current density of 1000 mA cm−2. This work not only represents an advancing step in the SC-SOFC field but also authenticates an effective codoping strategy for the design of a CO2-resistant cathode for low-temperature applications.

ChemElectroChem_5_2018_785_792.pdf

Lowering the operating temperature of solid oxide fuel cells (SOFCs) is highly desirable to reduc... more Lowering the operating temperature of solid oxide fuel cells (SOFCs) is highly desirable to reduce the cost and increase the lifetime, which relies upon the development of a cathode component with high oxygen reduction reaction (ORR) activity at a lower temperature. Herein, we report the characterization of high-performance BaSc x Co 1-x O 3-d (x = 0, 0.125, 0.25, and 0.375) perovskite SOFC cathodes. Unlike BaCoO 3-d , which adopts 2Hhexagonal perovskite structure, the replacement of 25 mol % of Co with Sc stabilizes the cubic structure, which also leads to the significant reduction in area specific resistances and their activation energies between 650 and 500 8C (for BaSc 0.25 Co 0.75 O 3d ) relative to the non-doped BaCoO 3-d . In this temperature range, BaSc 0.25 Co 0.75 O 3-d displayed a remarkably high ORR activity compared to Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-d (BSCF), the current cathode benchmark. We attribute such superior ORR performance to the higher oxygen non-stoichiometries of BaSc 0.25 Co 0.75 O 3-d relative to BSCF, which also translates to the higher oxygen bulk diffusion and surface exchange coefficients for the former compared to the latter. As a result, a single fuel cell based on an anode-supported 20 mm thick samarium-doped ceria electrolyte and BaSc 0.25 Co 0.75 O 3-d cathode achieved a very high peak power density of 1723 mW cm À2 at 650 8C. We also demonstrated the possibility to increase the ORR activity of the BaSc 0.25 Co 0.75 O 3-d cathode by impregnation of a low amount of silver.

Inter J Energy Res_42_2018_1551_1562.pdf

Lowering CO 2 emissions has become one of the key drivers behind the process intensification and ... more Lowering CO 2 emissions has become one of the key drivers behind the process intensification and modification in current chemical process industries. Here, we proposed a graphical method that features simultaneous correlation between CO 2 emission reduction, fuel switching, energy saving, investment cost, carbon credit, and payback time. Such CO 2 emission reduction can be obtained by fuel switching and/or retrofitting of the heat exchanger network.

Perovskite-based mixed protonic–electronic conducting membranes for hydrogen separation: Recent status and advances

Hydrogen share in the energy market has increased significantly in line with greater demand for z... more Hydrogen share in the energy market has increased significantly in line with greater demand for zero emission fuel and the development of novel production routes via renewable resources. The application of mixed protonic–electronic conducting (MPEC) ceramic membrane within the hydrogen production process is an innovative route that enables high purity hydrogen production with low cost. This review provides readers a brief summary of the research efforts on MPEC ceramic membrane for hydrogen separation as well as the membrane reactor for hydrogen production and dehydrogenation or hydrogenation reactions. Most of the existing MPEC ceramic membranes come from either a single-phase or a dual-phase membrane. We discuss the working principles, the performances, the advantages and disadvantages, and the main issues of all these membranes. Major emphasis of the review is to cover the literature published in the last ten years since the earlier progress has been well documented by the previously existing reviews. We also put forward recommendations for future research direction in this topic.

Nanostructured Co-Mn containing perovskites for degradation of pollutants: Insight into the activity and stability

The efficient oxidative removal of persistent organic components in wastewater relies on low-cost... more The efficient oxidative removal of persistent organic components in wastewater relies on low-cost heterogeneous catalysts that offer high catalytic activity, stability, and recyclability. Here, we designed a series of nanos-tructured Co-Mn containing perovskite catalysts, LaCo1−xMnxO3+δ (LCM, x = 0, 0.3, 0.5, 0.7, and 1.0), with over-stoichiometric oxygen (δ > 0) to show superior catalytic activity for the degradation of a variety of persistent aqueous organic pollutants by activating peroxymonosulfate (PMS). The nature of LCM for catalysis was comprehensively investigated. A " volcano-shaped " correlation was observed between the catalytic activity and electron filling (e g) of Co in LCM. Among these compounds, LaCo0.5Mn0.5O3+δ (LCM55) exhibited an excellent activity with eg = 1.27. The high interstitial oxygen ion diffusion rate (D O 2− = 1.58 ± 0.01 × 10−13 cm2 s−1) of LCM55 also contributes to its catalytic activity. The enhanced stability of LCM55 can be ascribed to its stronger relative acidity (3.22). Moreover, an increased solution pH (pH ≥ 7) generated a faster organic degradation rate and a decrease in metal leaching (0.004 mM) for LCM55 perovskite, justifying it as a potential material for environmental remediation.

3D ordered macroporous SmCoO3 perovskite for highly active and selective hydrogen peroxide detection

We reported the direct electrochemical hydrogen peroxide detection on three-dimensionally ordered... more We reported the direct electrochemical hydrogen peroxide detection on three-dimensionally ordered macroporous SmCoO3 (3DOM-SmCoO3) perovskite oxide electrode synthesized via a poly (methyl methacrylate) (PMMA) colloidal crystal templating route. The low-cost and simple 3DOM-SmCoO3 sensor not only overcome the various disadvantages of enzyme-and noble metal-based sensors but also display a superior sensing performance for H2O2 detection. More importantly, using 800 nm PMMA microspheres, a hexagonally ordered macroporous crystalline structure can be created, which features large surface area (20.14 m2 g-1) and large, open, interconnected channels for facile reactants and ions diffusions. The resultant 3DOM-SmCoO 3 synthesized using 800 nm PMMA microspheres template (3D-SC-800) displayed higher sensitivity (715 and 460 mA mM-1 cm-2), lower limit of detection (0.004 mM), larger detection linear range (0.1-10,000 mM), and higher selectivity in the presence of interfering species (i.e., glucose, ascorbic acid, dopamine, and uric acid), for H2O2 detection, relative to SmCoO3 (SC) and SmCoO3 synthesized using 200 nm PMMA template (3D-SC-200). Our comprehensive electro-chemical characterization attributes the superior H2O2 electrooxidation performance of 3D-SC-800 to its fast electron transfer kinetics and diffusion rate. What we demonstrated here bolsters the future opportunity to harness ordered macroporous perovskite oxide-based materials for highly active and selective non-enzymatic H2O2 detection.

Recent progress on advanced materials for solid-oxide fuel cells operating below 500 °C

Adv Mater_29_2017_1700132_1_33_Inside Back Cover Picture.pdf

Modeling and optimization of refinery hydrogen network – a new strategy to linearize power equation of new compressor

Refinery hydrogen network problem is highly nonlinear due to the equation that describes the powe... more Refinery hydrogen network problem is highly nonlinear due to the equation that describes the power of new compressor. Most of the previous attempts to linearize this equation have been made by assuming constant suction and discharge pressure while taking the inlet flow rate as a variable. Such assumption may not be practical in real condition because the calculated power requirement for new compressor may not be compatible with the pressure ratio of the selected compressor. This work proposed a new linearization method for the power of new compressor that provides additional degree of freedom by allowing the solver to choose the optimum new compressor(s) that satisfied the pressure requirement of process sinks. Using our proposed model, mixed-integer nonlinear programming (MINLP) formulation can be converted into mixed-integer linear programming. The applicability of our model was validated using two different refinery case studies. Mixed-integer linear programming results obtained using our model require substantially lower computational cost than their MINLP counterparts where at least 60% savings in terms of iteration number and computational processing time were achieved. The approach demonstrated here can be potentially used to approach more complex refinery hydrogen network cases where the initial guess can be obtained from the linearized MINLP problem.

Perovskite-based proton conducting membranes for hydrogen separation: A review

Hydrogen is considered a fuel of the future due to its diversified supply and zero greenhouse gas... more Hydrogen is considered a fuel of the future due to its diversified supply and zero greenhouse gas emission. The application of advanced membrane technology for hydrogen separation within the larger hydrogen production process context can substitute the use of more expensive and energy intensive cryogenic distillation and pressure swing adsorption technologies. This review overviews the basic aspects and progresses in perovskite-based proton conducting hydrogen separation membranes. Different configurations such as symmetric, asymmetric, hollow fiber, and surface modified perovskite membranes with various compositions are discussed and summarized. The challenges and future directions of such membranes are also elaborated.

CO2 erosion of BaCo0.85Bi0.05Zr0.1O3-δ perovskite membranes under oxygen permeating conditions

CO2-resistant oxygen selective ceramic membranes have wide applications in clean energy delivery ... more CO2-resistant oxygen selective ceramic membranes have wide applications in clean energy delivery and green chemical synthesis. In this work, CO2 erosion and O2 permeation behavior of BaCo0.85Bi0.05Zr0.1O3-δ (BCBZ) perovskite hollow fibre membranes are investigated. The BCBZ hollow fibre was fabricated by a combined phase-inversion and sintering technique. Experimental results indicate that the O2 permeation flux can reach 3.07 mL cm−2 min−1 at 1000 °C under the air/Ar gradient whereas the O2 flux reduced significantly in CO2 presence depending on the CO2 concentration in the feed gas or sweep gas. The deteriorating effect of CO2 on the membrane performance in the feed side was more significant than when it was present in the permeate side. One of the BCBZ hollow fibre samples had been tested for more than 190 h; undergoing six thermal cycles from 700 to 1000 °C in different CO2-containing gas streams. With high CO2 concentrations up to 10 vol.% in both feed and permeate sides, no permeation was observed due to the strong CO2 adsorption on the membrane surface; however, the O2 flux can be completely recovered once the CO2 became absent in the gas atmosphere. When the membrane test was continued up to 180 h, the O2 flux value cannot be fully recovered and 9.6% of the original flux value was lost due to the carbonate salt formation. To get the quantitative information on the erosion rate, more membrane samples had been tested from 1 to −8 days in 10 vol.% CO2 at 900 °C under the oxygen permeating conditions. We found that the erosion rate was relatively fast at the beginning stage with corrosion depth up to 3 µm for the first 3 days but slowed down to 1 µm depth for the subsequent 5 days. The significantly reduced erosion rate is due to the higher O2 concentration in the locally uncontaminated membrane area (without the carbonate deposition). Inspired by such findings, one future strategy to protect the membrane is to deposit the membrane surface using more robust ion-conducting layer like Sm0.2Ce0.8O1.9 .

Revamping existing glycol technologies in natural gas dehydration to improve the purity and absorption efficiency: Available methods and recent developments

The glycol purity limit in conventional absorption-based natural gas dehydration process has led ... more The glycol purity limit in conventional absorption-based natural gas dehydration process has led to the significant water vapour presence in the supposedly dry product gas. Several alternative processes have been developed to overcome this limitation that includes stripping gas injection using nitrogen, a portion of dry product gas, or volatile hydrocarbon (DRIZO process), stripping gas modified with Stahl column, and Coldfinger technology. This review summarises these different processes and elaborates on their mechanisms, process flow diagram, advantages, drawbacks, and current statuses. Relevant works from 1991 to 2017 were compiled and the existing gaps were highlighted as recommendation for future work.

Modeling of hydrogen separation through porous YSZ hollow fiber-supported graphene oxide membrane

In this work, hydrogen (H2) permeation fluxes through 230 nm-thick graphene oxide (GO) membrane d... more In this work, hydrogen (H2) permeation fluxes through 230 nm-thick graphene oxide (GO) membrane deposited on porous YSZ hollow fiber were measured and correlated to an explicit H2 permeation model. H2 fluxes through such GO-YSZ hollow fiber membrane increased from 4.83 x 10-8 mol cm-2 s-1 to 2.11 x 10-7 mol cm-2 s-1 with temperature rise from 20 to 100 oC. The activation energy of H2 permeation was determined by the linear regression of the experimental data and was applied in the theoretical calculations. The model predictions fit well the temperature dependent and the argon sweep gas flow rate dependent H2 fluxes data. Using the derived permeation model, the effects of vacuum pressure at lumen side and H2 partial pressure at shell side, membrane area, and GO membrane film thickness on the membrane performance were simulated and discussed to provide insights for practical applications.

Active centers of catalysts for higher alcohol synthesis from syngas: A review

The gradual depletion of oil resources and the necessity to reduce greenhouse gas emissions portr... more The gradual depletion of oil resources and the necessity to reduce greenhouse gas emissions portray a concerning image of our contemporary security of liquid transportation fuels in the event of a global crisis. Despite a vast amount of natural gas resources that we have and the huge economic incentive, the conversion of gas to liquid fuels or chemicals is still very limited because of the high technological complexity and capital cost for facilities. However, with the anticipated depletion of liquid petroleum and the soaring price of crude oil, the conversion of natural gas to liquid feedstock or fuels will become more and more important. Higher alcohols are important feedstocks for the chemical and pharmaceutical industries and have wide applications as potential fuel additives or hydrogen carriers for fuel cells for clean energy delivery. There is a long-standing interest in the synthesis of higher alcohols from syngas, an important Fischer−Tropsch technology for natural gas conversion. The purpose of this review is to provide readers with an extensive account of catalytic synthesis of higher alcohols from syngas using various catalysts reviewed from a unique perspective: clarification of the active centers and reaction pathways. In light of the different sources providing the active centers, three major classes of catalysts in terms of monometallic, bimetallic, and trimetallic/multimetallic catalysts are systematically reviewed, and their respective performances are carefully compared. Finally, future works proposed to improve the catalyst design are described.

New phosphorus-doped perovskite oxide as an oxygen reduction reaction electrocatalyst in an alkaline solution

Because of their structural and compositional flexibility, perovskite oxides represent an attract... more Because of their structural and compositional flexibility, perovskite oxides represent an attractive alternative electrocatalyst class to precious metals for the oxygen reduction reaction(ORR); an important reaction in fuel cells and metal–air batteries. Partial replacement of the original metal cation with another cation ,namely, doping, can be used to tailor the ORR activity of perovskite, for which a metal has been exclusively used as the dopant component in the past. Herein, phosphorus is proposed as a non-metal dopant for the cation site to develop a new perovskite family with the formula of La0.8Sr0.2Mn1-xPxO3-d (x = 0, 0.02, 0.05, and 0.1; denoted as LSM, LSMP0.02, LSMP0.05, and LSMP0.1, respectively). Powder XRD patterns reveal that the solubility of phosphorus in the perovskite structure is around 0 .05. Rotating ring-disk electrode experiments in the form of linear-sweep voltammetry scans demonstrated the best ORR performance for LSMP0.05, and also revealed close to a four-electron ORR pathway for all four compositions. A chronoamperometric test (9000 s) and 500 cycle accelerated durability test demonstrated higher durability for LSMP0.05 relative to that of LSM and the commercial 20 wt %Pt/C catalyst. The higher ORR activity for LSMP0.05 is attributed to the optimised average valence of Mn, as evidenced by combined X-ray photoelectron spectroscopy and soft X-ray absorption spectroscopy data. Doping phosphorus into perovskites is an effective way to develop high-performance electrocatalysts for ORR.

Towards enhanced energy density of graphene-based supercapacitors: Current status, approaches, and future directions

Despite high power density, fast charging/discharging rate, and long operational lifetime, large-... more Despite high power density, fast charging/discharging rate, and long operational lifetime, large-scale application of supercapacitor (SC) is limited by its intrinsically low energy densities (of 5–8 Wh kg−1 (gravimetric) and 5–8 Wh L−1 (volumetric)), which are at least 10-fold lower than battery. Since the invention of graphene in 2004, graphene-based SCs have set the upper performance limit of the symmetric carbon-based SCs due to superior electrical conductivity and very high accessible surface area of graphene. Still, only two companies have commercialised graphene-based supercapacitors thus far. Their maximum achievable energy density (i.e., 11.65 Wh kg−1) is too low to make them competitive against batteries in high-energy applications. To this end, this comprehensive review focuses on the material- and device-level approaches to high energy density graphene-based conventional macroscale SCs (≥11.65 Wh kg−1) and flexible SCs and microsupercapacitors (≈0.3–10 mWh cm−3; ≈300–16000 μWh cm−2). It includes a description on how each approach is implemented and an explanation of how each can provide effective research results. This review also meticulously discusses the underlying challenges and possible solutions to achieve high energy density graphene-based SCs in practice.

Mixed protonic-electronic conducting perovskite oxide as a robust oxygen evolution reaction catalyst

Large-scale utilization of hydro, solar, or wind-based electrochemical water splitting relies on ... more Large-scale utilization of hydro, solar, or wind-based electrochemical water splitting relies on the availability of low cost, highly active oxygen evolution reaction (OER) catalyst. Transition metal-containing perovskite oxide is attractive in this regard. The OER on such perovskite oxide in an alkaline solution is nonetheless often limited by proton transfer step. To overcome such limitation, here we apply mixed protonic-electronic conductor BaCo0.8-xFexZr0.1Y0.1O3 (x = 0, 0.2, and 0.4) as an OER catalyst. Among these three, BaCo0.8Zr0.1Y0.1O3 (BC0.8ZY) in particular shows the lowest OER overpotential, the lowest Tafel slope, the highest OER mass activity, and the highest OER specific activity, which surpass those of Ba0.5Sr0.5Co0.8Fe0.2O3-d (BSCF) benchmark. Using O2-temperature programmed desorption, impedance spectroscopy, and O1s X-ray photoelectron spectroscopy, we attribute such superior OER performance to the highest oxygen desorption capacity, the lowest charge transfer resistance, and the highest hydroxide species content for BC0.8ZY. We also demonstrate that the OER current of BC0.8ZY exhibits a first-reaction order dependence to the solution pH between 12.5 and 14, which confirms its proton transfer rate-determining step.

Chem Eng Res Des_134_2018_487_496.pdf

Hollow fiber Membrane Oxygen permeation a b s t r a c t Oxygen-selective perovskite hollow fiber ... more Hollow fiber Membrane Oxygen permeation a b s t r a c t Oxygen-selective perovskite hollow fiber membrane can be used to obtain an effective oxygen separation from air at high temperature (above 700 • C) for large scale application. Here, we display that oxygen permeation fluxes of La 0.6 Sr 0.4 CoO 3 (LSC 113 ) hollow fiber membrane was enhanced by macrostructure modification and (La,Sr) 2 CoO 4 (LSC 214 ) surface decoration. By changing the cross-section macrostructure from sandwich structure (for LSC-a fiber) to asymmetric structure (for LSC-b fiber), the oxygen flux was improved by up to 3.6-fold.

Carbon and non-carbon support materials for platinum-based catalysts in fuel cells

Carbon and other platinum-supporting materials have been studied as electrode catalyst component ... more Carbon and other platinum-supporting materials have been studied as electrode catalyst component of low-temperature fuel cells. Platinum (Pt) is commonly used as the catalyst due to its high electro-catalytic activity. Current research is now focusing on using either modified carbon-based or non-carbon-based materials as catalyst supports to enhance the catalytic performance of Pt. In recent years, Pt and Pt-alloy catalysts supported on modified carbon-based and non-carbon-based materials have received remarkable interests due to their significant properties that can contribute to the excellent fuel cell performance. Thus, it is timely to review this topic, focusing on various modified carbon-based supports and their advantages, limitations and future prospects. Non-carbon-based support for Pt and Pt-alloy catalysts will also be discussed. Firstly, this review summarises the progress to date in the development of these catalyst support materials; from carbon black to the widely explored catalyst support, graphene. Secondly, a comparison and discussion of each catalyst support in terms of morphology, electro-catalytic activity, structural characteristics , and its fuel cell performance are emphasized. All the catalyst support materials reviewed are considered to be promising, high-potential candidates that may find commercial value as catalyst support materials for fuel cells. Finally, a brief discussion on cost relating Pt based catalyst for mass production is included.

Systematic study of oxygen evolution activity and stability on La1−xSrxFeO3−δ perovskite electrocatalysts in alkaline media

Perovskite oxide is an attractive low-cost alternative catalyst for oxygen evolution reaction (OE... more Perovskite oxide is an attractive low-cost alternative catalyst for oxygen evolution reaction (OER) relative to the precious metal oxide-based electrocatalysts (IrO2 and RuO2). In this work, a series of Sr-doped La-based perovskite oxide catalysts with compositions of La1−xSrxFeO3−δ (x = 0, 0.2, 0.5, 0.8, and 1) are synthesized and characterized. The OER-specific activities in alkaline solution increase in the order of LaFeO3−δ (LF), La0.8Sr 0.2FeO3−δ (LSF-0.2), La0.5Sr0.5FeO3−δ (LSF-0.5), SrFeO3−δ (SF), and La0.2Sr0.8FeO3−δ (LSF-0.8). We establish a direct correlation between the enhancement in the specific activity and the amount of surface oxygen vacancies as well as the surface Fe oxidation states. The improved specific activity for LSF-0.8 is clearly linked to the optimum amount of surface oxygen vacancies and surface Fe oxidation states. We also find that the OER performance stability is a function of the crystal structure and the deviation in the surface La and/or Sr composition(s) from their bulk stoichiometric compositions. The cubic structure and lower deviation, as is the case for LSF-0.8, led to a higher OER performance stability. These surface performance relations provide a promising guideline for constructing efficient water oxidation.

Significantly improving the durability of single-chamber solid oxide fuel cells: A highly active CO2‑resistant perovskite cathode

The single-chamber solid oxide fuel cell (SC-SOFC) represents an attractive alternative to batter... more The single-chamber solid oxide fuel cell (SC-SOFC) represents an attractive alternative to batteries for micropower applications given its simplified stack design, easy gas management, lower operation temperature, and quicker start-up. Its stable operation over long duration relies on the availability of CO2-resistant cathode materials with high oxygen reduction reaction (ORR) activity. Here, we reported a novel perovskite oxide cathode SrSc 0.075 Ta 0.025 Fe 0.9 O 3−δ (SSTF75), which provides CO 2 resistance and high ORR activity. A peak power density of 1430 mW cm −2 was achieved with the SSTF75/Sm0.2Ce0.8O1.9 cathode at 650 °C with a methane and oxygen gas mixture (1:1 v/v ratio). It retained stable voltage performance at 600 °C for an over 90 h duration when discharged at a current density of 1000 mA cm−2. This work not only represents an advancing step in the SC-SOFC field but also authenticates an effective codoping strategy for the design of a CO2-resistant cathode for low-temperature applications.

ChemElectroChem_5_2018_785_792.pdf

Lowering the operating temperature of solid oxide fuel cells (SOFCs) is highly desirable to reduc... more Lowering the operating temperature of solid oxide fuel cells (SOFCs) is highly desirable to reduce the cost and increase the lifetime, which relies upon the development of a cathode component with high oxygen reduction reaction (ORR) activity at a lower temperature. Herein, we report the characterization of high-performance BaSc x Co 1-x O 3-d (x = 0, 0.125, 0.25, and 0.375) perovskite SOFC cathodes. Unlike BaCoO 3-d , which adopts 2Hhexagonal perovskite structure, the replacement of 25 mol % of Co with Sc stabilizes the cubic structure, which also leads to the significant reduction in area specific resistances and their activation energies between 650 and 500 8C (for BaSc 0.25 Co 0.75 O 3d ) relative to the non-doped BaCoO 3-d . In this temperature range, BaSc 0.25 Co 0.75 O 3-d displayed a remarkably high ORR activity compared to Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-d (BSCF), the current cathode benchmark. We attribute such superior ORR performance to the higher oxygen non-stoichiometries of BaSc 0.25 Co 0.75 O 3-d relative to BSCF, which also translates to the higher oxygen bulk diffusion and surface exchange coefficients for the former compared to the latter. As a result, a single fuel cell based on an anode-supported 20 mm thick samarium-doped ceria electrolyte and BaSc 0.25 Co 0.75 O 3-d cathode achieved a very high peak power density of 1723 mW cm À2 at 650 8C. We also demonstrated the possibility to increase the ORR activity of the BaSc 0.25 Co 0.75 O 3-d cathode by impregnation of a low amount of silver.

Inter J Energy Res_42_2018_1551_1562.pdf

Lowering CO 2 emissions has become one of the key drivers behind the process intensification and ... more Lowering CO 2 emissions has become one of the key drivers behind the process intensification and modification in current chemical process industries. Here, we proposed a graphical method that features simultaneous correlation between CO 2 emission reduction, fuel switching, energy saving, investment cost, carbon credit, and payback time. Such CO 2 emission reduction can be obtained by fuel switching and/or retrofitting of the heat exchanger network.

Perovskite-based mixed protonic–electronic conducting membranes for hydrogen separation: Recent status and advances

Hydrogen share in the energy market has increased significantly in line with greater demand for z... more Hydrogen share in the energy market has increased significantly in line with greater demand for zero emission fuel and the development of novel production routes via renewable resources. The application of mixed protonic–electronic conducting (MPEC) ceramic membrane within the hydrogen production process is an innovative route that enables high purity hydrogen production with low cost. This review provides readers a brief summary of the research efforts on MPEC ceramic membrane for hydrogen separation as well as the membrane reactor for hydrogen production and dehydrogenation or hydrogenation reactions. Most of the existing MPEC ceramic membranes come from either a single-phase or a dual-phase membrane. We discuss the working principles, the performances, the advantages and disadvantages, and the main issues of all these membranes. Major emphasis of the review is to cover the literature published in the last ten years since the earlier progress has been well documented by the previously existing reviews. We also put forward recommendations for future research direction in this topic.

Nanostructured Co-Mn containing perovskites for degradation of pollutants: Insight into the activity and stability

The efficient oxidative removal of persistent organic components in wastewater relies on low-cost... more The efficient oxidative removal of persistent organic components in wastewater relies on low-cost heterogeneous catalysts that offer high catalytic activity, stability, and recyclability. Here, we designed a series of nanos-tructured Co-Mn containing perovskite catalysts, LaCo1−xMnxO3+δ (LCM, x = 0, 0.3, 0.5, 0.7, and 1.0), with over-stoichiometric oxygen (δ > 0) to show superior catalytic activity for the degradation of a variety of persistent aqueous organic pollutants by activating peroxymonosulfate (PMS). The nature of LCM for catalysis was comprehensively investigated. A " volcano-shaped " correlation was observed between the catalytic activity and electron filling (e g) of Co in LCM. Among these compounds, LaCo0.5Mn0.5O3+δ (LCM55) exhibited an excellent activity with eg = 1.27. The high interstitial oxygen ion diffusion rate (D O 2− = 1.58 ± 0.01 × 10−13 cm2 s−1) of LCM55 also contributes to its catalytic activity. The enhanced stability of LCM55 can be ascribed to its stronger relative acidity (3.22). Moreover, an increased solution pH (pH ≥ 7) generated a faster organic degradation rate and a decrease in metal leaching (0.004 mM) for LCM55 perovskite, justifying it as a potential material for environmental remediation.

3D ordered macroporous SmCoO3 perovskite for highly active and selective hydrogen peroxide detection

We reported the direct electrochemical hydrogen peroxide detection on three-dimensionally ordered... more We reported the direct electrochemical hydrogen peroxide detection on three-dimensionally ordered macroporous SmCoO3 (3DOM-SmCoO3) perovskite oxide electrode synthesized via a poly (methyl methacrylate) (PMMA) colloidal crystal templating route. The low-cost and simple 3DOM-SmCoO3 sensor not only overcome the various disadvantages of enzyme-and noble metal-based sensors but also display a superior sensing performance for H2O2 detection. More importantly, using 800 nm PMMA microspheres, a hexagonally ordered macroporous crystalline structure can be created, which features large surface area (20.14 m2 g-1) and large, open, interconnected channels for facile reactants and ions diffusions. The resultant 3DOM-SmCoO 3 synthesized using 800 nm PMMA microspheres template (3D-SC-800) displayed higher sensitivity (715 and 460 mA mM-1 cm-2), lower limit of detection (0.004 mM), larger detection linear range (0.1-10,000 mM), and higher selectivity in the presence of interfering species (i.e., glucose, ascorbic acid, dopamine, and uric acid), for H2O2 detection, relative to SmCoO3 (SC) and SmCoO3 synthesized using 200 nm PMMA template (3D-SC-200). Our comprehensive electro-chemical characterization attributes the superior H2O2 electrooxidation performance of 3D-SC-800 to its fast electron transfer kinetics and diffusion rate. What we demonstrated here bolsters the future opportunity to harness ordered macroporous perovskite oxide-based materials for highly active and selective non-enzymatic H2O2 detection.

Recent progress on advanced materials for solid-oxide fuel cells operating below 500 °C

Adv Mater_29_2017_1700132_1_33_Inside Back Cover Picture.pdf

Modeling and optimization of refinery hydrogen network – a new strategy to linearize power equation of new compressor

Refinery hydrogen network problem is highly nonlinear due to the equation that describes the powe... more Refinery hydrogen network problem is highly nonlinear due to the equation that describes the power of new compressor. Most of the previous attempts to linearize this equation have been made by assuming constant suction and discharge pressure while taking the inlet flow rate as a variable. Such assumption may not be practical in real condition because the calculated power requirement for new compressor may not be compatible with the pressure ratio of the selected compressor. This work proposed a new linearization method for the power of new compressor that provides additional degree of freedom by allowing the solver to choose the optimum new compressor(s) that satisfied the pressure requirement of process sinks. Using our proposed model, mixed-integer nonlinear programming (MINLP) formulation can be converted into mixed-integer linear programming. The applicability of our model was validated using two different refinery case studies. Mixed-integer linear programming results obtained using our model require substantially lower computational cost than their MINLP counterparts where at least 60% savings in terms of iteration number and computational processing time were achieved. The approach demonstrated here can be potentially used to approach more complex refinery hydrogen network cases where the initial guess can be obtained from the linearized MINLP problem.