Objectives Develop materials and components and optimize operating conditions of the direct metha... more Objectives Develop materials and components and optimize operating conditions of the direct methanol fuel cell (DMFC) for maximum power density and fuel conversion efficiency at a minimum cost. In particular: • Design and optimize membrane-electrode assemblies (MEAs) to enhance cell performance. • Advance electrocatalysis of methanol oxidation and oxygen reduction to increase power density and lower total precious metal loading. • Characterize and optimize non-Nafion polymers with reduced crossover and improved performance. • Model, develop and demonstrate practical viability of advanced cell components. Approach • Build, operate and test performance of DMFCs with different anode and cathode catalysts, membranes and MEAs. • Through experimentation, develop thorough understanding of the key factors impacting cell performance and durability. • Maximize efficiency, power and energy density of DMFCs by creative designing of stack components and experimental verification of the hardware ...
It is generally accepted that Pt-Ru alloy catalysts with an atomic Pt-to-Ru ratio of 1:1 generate... more It is generally accepted that Pt-Ru alloy catalysts with an atomic Pt-to-Ru ratio of 1:1 generate the best anode perform'ance in the direct methanol fuel cell (DMFG). However, at near-ambient cell operating temperatures, Gasteiger et al. reported that a catalyst with significantly lower Ru content, 10 at %, offers the highest activity towards methanol. Recently, Dinh et al. demonstrated that the activity of different Pt-Ru catalysts with the same Pt-to-Ru atomic ratio in the bulk might vary depending on the actual surface composition, which is often significantly different from that in the bulk phase, In this work, we study several experimental Pt-Ru catalysts (Johnson Matthey) with Pt-to-Ru atomic ratio ranging from 9: 1 to 1 :2. Electrocatalytic activity of these catalysts in methanol oxidation reaction is investigated in a regular DMFC 'and probed using voltammetric stripping of surhce CO.
The main research objective is to develop materials, cell components and optimize operating condi... more The main research objective is to develop materials, cell components and optimize operating conditions of direct methanol fuel cells for maximum power density and fuel conversion efficiency at a minimum cost. Individual objectives include:
This contribution describes the operation of a pilot plant for the production of 3-exomethylene-7... more This contribution describes the operation of a pilot plant for the production of 3-exomethylene-7(R)-glutaroylaminocepham-4-carboxylic acid 1(S)-oxide (4a) by the electrochemical reduction of 3-acetoxymethyl-7(R)-glutaroylaminoceph-3-em-4-carboxylic acid 1(S)-oxide ...
ABSTRACT High-resolution porous structures of catalyst layer (CL) with multicomponent in proton e... more ABSTRACT High-resolution porous structures of catalyst layer (CL) with multicomponent in proton exchange membrane fuel cells are reconstructed using a reconstruction method called quartet structure generation set. Characterization analyses of nanoscale structures are implemented including pore size distribution, specific area and phase connectivity. Pore-scale simulation methods based on the lattice Boltzmann method are developed and used to predict the macroscopic transport properties including effective diffusivity and proton conductivity. Nonuniform distributions of ionomer in CL generates more tortuous pathway for reactant transport and greatly reduces the effective diffusivity. Tortuosity of CL is much higher than conventional Bruggeman equation adopted. Knudsen diffusion plays a significant role in oxygen diffusion and significantly reduces the effective diffusivity. Reactive transport inside the CL is also investigated. Although the reactive surface area of non-precious metal catalyst (NPMC) CL is much higher than that of Pt CL, the oxygen reaction rate is quite lower in NPMC CL compared with that in Pt CL, due to much lower reaction rate. Micropores (a few nanometers) in NPMC CL although can increase reactive sites, contribute little to enhance the mass transport. Mesopores (few tens of nanometers) or macropores are required to increase the mass transport rate.
ABSTRACT We focus in this paper on the reduction of catalyst loading in direct methanol fuel cell... more ABSTRACT We focus in this paper on the reduction of catalyst loading in direct methanol fuel cells currently under development at Los Alamos National Laboratory. Based on single-cell DMFC testing, we discuss performance vs. catalyst loading trade-offs and ...
This paper describes an anode model for the direct methanol fuel cell (DMFC). It is a steady stat... more This paper describes an anode model for the direct methanol fuel cell (DMFC). It is a steady state, isothermal model, in which electrochemical reaction rates are governed by the Tafel kinetics. Mass transfer and diffusion are considered in the transport equations. The main purpose of the model is to calculate the anode potential loss and methanol crossover current density using cell current density, concentration and flow rate of methanol as inputs. The model also calculates the flux of methanol at the exit of the anode, as well as methanol concentration at the anode catalyst layer and at the membrane-catalyst interface.
Commercialization of fuel cells has become increasingly important over the past several years. On... more Commercialization of fuel cells has become increasingly important over the past several years. One of the major obstacles facing potential fuel cell manufacturers is quality and cost of raw materials (1) . While much effort has focused on membrane and catalyst cost factors, the work that has been done regarding other fuel cell stack components has been more limited. The selection of appropriate materials used to form the bipolar plates of a stack can have significant impact on stack cost, performance, and longevity.
Objectives Develop materials and components and optimize operating conditions of the direct metha... more Objectives Develop materials and components and optimize operating conditions of the direct methanol fuel cell (DMFC) for maximum power density and fuel conversion efficiency at a minimum cost. In particular: • Design and optimize membrane-electrode assemblies (MEAs) to enhance cell performance. • Advance electrocatalysis of methanol oxidation and oxygen reduction to increase power density and lower total precious metal loading. • Characterize and optimize non-Nafion polymers with reduced crossover and improved performance. • Model, develop and demonstrate practical viability of advanced cell components. Approach • Build, operate and test performance of DMFCs with different anode and cathode catalysts, membranes and MEAs. • Through experimentation, develop thorough understanding of the key factors impacting cell performance and durability. • Maximize efficiency, power and energy density of DMFCs by creative designing of stack components and experimental verification of the hardware ...
It is generally accepted that Pt-Ru alloy catalysts with an atomic Pt-to-Ru ratio of 1:1 generate... more It is generally accepted that Pt-Ru alloy catalysts with an atomic Pt-to-Ru ratio of 1:1 generate the best anode perform'ance in the direct methanol fuel cell (DMFG). However, at near-ambient cell operating temperatures, Gasteiger et al. reported that a catalyst with significantly lower Ru content, 10 at %, offers the highest activity towards methanol. Recently, Dinh et al. demonstrated that the activity of different Pt-Ru catalysts with the same Pt-to-Ru atomic ratio in the bulk might vary depending on the actual surface composition, which is often significantly different from that in the bulk phase, In this work, we study several experimental Pt-Ru catalysts (Johnson Matthey) with Pt-to-Ru atomic ratio ranging from 9: 1 to 1 :2. Electrocatalytic activity of these catalysts in methanol oxidation reaction is investigated in a regular DMFC 'and probed using voltammetric stripping of surhce CO.
The main research objective is to develop materials, cell components and optimize operating condi... more The main research objective is to develop materials, cell components and optimize operating conditions of direct methanol fuel cells for maximum power density and fuel conversion efficiency at a minimum cost. Individual objectives include:
This contribution describes the operation of a pilot plant for the production of 3-exomethylene-7... more This contribution describes the operation of a pilot plant for the production of 3-exomethylene-7(R)-glutaroylaminocepham-4-carboxylic acid 1(S)-oxide (4a) by the electrochemical reduction of 3-acetoxymethyl-7(R)-glutaroylaminoceph-3-em-4-carboxylic acid 1(S)-oxide ...
ABSTRACT High-resolution porous structures of catalyst layer (CL) with multicomponent in proton e... more ABSTRACT High-resolution porous structures of catalyst layer (CL) with multicomponent in proton exchange membrane fuel cells are reconstructed using a reconstruction method called quartet structure generation set. Characterization analyses of nanoscale structures are implemented including pore size distribution, specific area and phase connectivity. Pore-scale simulation methods based on the lattice Boltzmann method are developed and used to predict the macroscopic transport properties including effective diffusivity and proton conductivity. Nonuniform distributions of ionomer in CL generates more tortuous pathway for reactant transport and greatly reduces the effective diffusivity. Tortuosity of CL is much higher than conventional Bruggeman equation adopted. Knudsen diffusion plays a significant role in oxygen diffusion and significantly reduces the effective diffusivity. Reactive transport inside the CL is also investigated. Although the reactive surface area of non-precious metal catalyst (NPMC) CL is much higher than that of Pt CL, the oxygen reaction rate is quite lower in NPMC CL compared with that in Pt CL, due to much lower reaction rate. Micropores (a few nanometers) in NPMC CL although can increase reactive sites, contribute little to enhance the mass transport. Mesopores (few tens of nanometers) or macropores are required to increase the mass transport rate.
ABSTRACT We focus in this paper on the reduction of catalyst loading in direct methanol fuel cell... more ABSTRACT We focus in this paper on the reduction of catalyst loading in direct methanol fuel cells currently under development at Los Alamos National Laboratory. Based on single-cell DMFC testing, we discuss performance vs. catalyst loading trade-offs and ...
This paper describes an anode model for the direct methanol fuel cell (DMFC). It is a steady stat... more This paper describes an anode model for the direct methanol fuel cell (DMFC). It is a steady state, isothermal model, in which electrochemical reaction rates are governed by the Tafel kinetics. Mass transfer and diffusion are considered in the transport equations. The main purpose of the model is to calculate the anode potential loss and methanol crossover current density using cell current density, concentration and flow rate of methanol as inputs. The model also calculates the flux of methanol at the exit of the anode, as well as methanol concentration at the anode catalyst layer and at the membrane-catalyst interface.
Commercialization of fuel cells has become increasingly important over the past several years. On... more Commercialization of fuel cells has become increasingly important over the past several years. One of the major obstacles facing potential fuel cell manufacturers is quality and cost of raw materials (1) . While much effort has focused on membrane and catalyst cost factors, the work that has been done regarding other fuel cell stack components has been more limited. The selection of appropriate materials used to form the bipolar plates of a stack can have significant impact on stack cost, performance, and longevity.
Uploads
Papers by Piotr Zelenay