With the advances in characterization techniques, various operando/in-situ methods were applied i... more With the advances in characterization techniques, various operando/in-situ methods were applied in studying rechargeable batteries in order to improve the electrochemical properties of electrode materials, prolonging the battery life and developing new battery materials. In the present review, we focus on the characterization of electrode materials with operando/in-situ X-ray diffraction and Raman spectroscopies. By correlating the results obtained via these two techniques in different electrode chemistry: (a) intercalation materials, such as layered metal oxides and (b) conversion materials, such as elemental sulfur. We demonstrate the importance of using operando/in-situ techniques in examining the microstructural changes of the electrodes under various operating conditions, in both macro and micro-scales. These techniques also reveal the working and the degradation mechanisms of the electrodes and the possible side reactions involved. The comprehension of these mechanisms is fundamental for ameliorating the electrode materials, enhancing the battery performance and lengthening its cycling life.
An interpretation has been put forward of the fact that chloride ions have deleterious effects on... more An interpretation has been put forward of the fact that chloride ions have deleterious effects on the anodie passivation of AI, Fe, Cr and Fe-Cr alloys whereas some other metals such as Ti, Ta, Mo, W, and Zr do not lose their passivity on anodization in solutions containing chloride ions. The ideas put forward involve use of solid state concepts and considerations of coordination chemistry. It has been shown that high. metal-metal bond energies and high lattice energies of metal oxides are responsible for lesser tendency of metal ions of Ti, Ta, Mo, W and Zr to leave the lattice of the corresponding metal or metal-oxide, respectively. Further, even when their atoms or ions do find their way into the solution, they are irreversibly stabilized by the formation of stable complexes of "inner orbital" type, in terms of Taube's classification. Opposite considerations apply for the case of easily corroding metals such as AI, Fe, Cr and Fe-Cr alloys. Exceptionally easy tendency of aluminium to corrode on anodization in presence of a variety of anions has also been discussed in terms of the foregoing and other related concepts. A possible hypothetical scheme for the pitting corrosion of Al, Fe, etc., has also been mentioned. R6sum6-On avance une interpretation du fait que les ions de chlorure ont des effets delterioniques sur la passivit6 anodique de rAl, Fe, Cr et des alliages Fe-Cr, tandis que d'autres m6taux tels que le Ti, Ta, Mo, W et Zr gardent leur passivit6 devant des solutions anodisantes contenant des ions de chlorure. Leg th6ories avanc6es comprerment l'utilisation de concepts de semi-conduction et des considerations sur la chimie des coordinations. On a d6montr6 que les hautes 6nergies d6velopp~es par les combinaisons m6tal-m6tal et les ~nergies des oxydes m6talliques sont responsables d'une r~duction de la tendance des ions de ces m~taux h s'~happer. De plus, m~me lorsque leurs atomes ou leurs ions trouvent un passage dans la solution, ils sont irr6versiblement stabilis6s par la formation de complexes stables du type "orbite int6rieure", selon la classification de Taube. Des consid6rations oppos6es s'appliquent aux cas des m~taux facilement corrod6s tels que AI, Fe, Cr, ainsi que leg alliages Fe-Cr. On a 6tudi6 aussi la tendance tr~s prononc~e de l'aluminium ~ se corroder en anodisation en presence de divers anions sous forme des concepts precedents et autres. On mentionne aussi un syst~me th6orique possible pour la corrosion par points de ralumlnium, du fer, etc. Zusammenfassung-Es wird eine Erkl~rung dafiir gegeben, dab C1-die anodische Passivierung yon AI, Fe, Cr und FeCr-Legierungen behindert, wogegen einige andere Metalle wie Ti, Ta, Mo, W und Zr ihre anodische Passivierung in CI-haltigen L6sungen nicht verlieren. Als Grundlage dienen Vorstellungen iiber FestkOrper-und Koordinationschemie. Es wird gezeigt, dab starke Metall-Metall-Bindungen und hohe Gitterenergien der Metalle und Metalloxyde die geringere Neigung der Metallionen des Ti, Ta, Mo, W und Cr zum Austritt aus ihrem MetaU-oder Metalloxydgitter verursachem Auch wenn Ionen dieser Metalle in die L6sung iibertreten, werden sic durch die Bildung stabiler Innerer Orbitalkomplexe irreversibel stabilisiert, wobei die Darstellungsweise yon Taube angewendet v, ird. Entgegengesetzte 0berlegungen gelten fiir die CI-empfindlichen Metalle wie A1, Fe und Cr und FeCr-Legierungen. Die auBerordentlich hohe Tendenz des Aluminiums, bei anodischer Polarisation in Gegenwart einer Reihe yon Anionen zu korrodieren, kann mit den gleichea und fihnlichen Vorstellungen gedeutet werden. Eine Hypothese fiir den Ablauf der LochfraBkorrosion yon AI, Fe uses. wird angegeben.
Recent ideas of Fehlner and Mott on low-temperature oxidation, both thermal and anodic, are exami... more Recent ideas of Fehlner and Mott on low-temperature oxidation, both thermal and anodic, are examined with regard to the magnitudes of metal-metal and metal-oxygen bond strengths and their involvment in the interpretations of oxidation behavior of metals and semiconductors. It is pointed out that the magnitudes of bond strengths used by them appear to be inconsistent with the estimates of other workers based on well-established procedures. Some possible consequences of the reevaluated M-M and M-O bond strengths as regards the oxidation characteristics of metals are briefly mentioned. Also discussed is the influence of the estimated semiconductivity of anodization oxides on the subsequent anodic behavior of these metals.
There are many areas of chemistry that draw heavily upon and interact strongly with the correspon... more There are many areas of chemistry that draw heavily upon and interact strongly with the corresponding advances in physics and which, together, are called chemical physics. The more common examples of these areas are quantum chemistry, statistical thermodynamics, and the myriad forms of spectroscopy, etc. Similarly, there is one prominent field of physics, namely, solid-state physics, which has a profound influence on the development and progress of electrochemistry. The research endeavor on electrochemical problems which depend heavily upon the notions of solid-state physics for their proper elucidation is best grouped under electrochemical physics, in analogy with the chemical physics mentioned above.
The nature of factors that determine the electrochemical activities of metals for the M z÷ + ze-~... more The nature of factors that determine the electrochemical activities of metals for the M z÷ + ze-~ M reaction have been investigated. High activities of metals for this reaction are inversely related to their metal-metal bond energies and to their electrocatalytic activities for the hydrogen evolution reaction. The significance of these observations is discussed in relation to many other relevant factors, such as the electronic structure of metals, the ligand-field theory, the complex-forming affinities of metal ions, the activation energy for the exchange of water molecules from the first coordination sphere of the metal ions, the heat of hydration of M z÷ ions and the mechanism of pitting potentials of metals. Correlative trends that permit some generalizations regarding the electrochemical activities of metals for the M z÷ + ze-~ .-~ M reaction have been shown to exist and are discussed.
The adsorption of oxygen by phthalocyanines has been studied by temperature programmed desorption... more The adsorption of oxygen by phthalocyanines has been studied by temperature programmed desorption between-160 and 400°C. A desorption peak is observed at-140°C for copper yhthalocynnine and at-115°C for iron phthalocyanine. The assoriated activation energies of desorption are 7.5 and 9.8 kcal mole-' and these two peaks corrrspond to a first order kinetics of drsorption. These results constitute the first direct evidence on the lack of rupture of the bond beiween t\%-o oxygen atoms in the molecule adsorbed on phthalocyanines. Finally, an attempt is made IO rxaminr the mechanistic proposals on the electroreduction of oxygen on phthalocyanines in the light, of the present results.
Many materials of practical interest are either semiconducting or insulating in nature. One of th... more Many materials of practical interest are either semiconducting or insulating in nature. One of the most important quantities characterising these materials, therefore, is the energy bandgap. In the present article, procedures available for estimating the bandgaps of binary, inorganic materials from thermochemical and related data have been briefly reviewed with special emphasis on recent work.
With the advances in characterization techniques, various operando/in-situ methods were applied i... more With the advances in characterization techniques, various operando/in-situ methods were applied in studying rechargeable batteries in order to improve the electrochemical properties of electrode materials, prolonging the battery life and developing new battery materials. In the present review, we focus on the characterization of electrode materials with operando/in-situ X-ray diffraction and Raman spectroscopies. By correlating the results obtained via these two techniques in different electrode chemistry: (a) intercalation materials, such as layered metal oxides and (b) conversion materials, such as elemental sulfur. We demonstrate the importance of using operando/in-situ techniques in examining the microstructural changes of the electrodes under various operating conditions, in both macro and micro-scales. These techniques also reveal the working and the degradation mechanisms of the electrodes and the possible side reactions involved. The comprehension of these mechanisms is fundamental for ameliorating the electrode materials, enhancing the battery performance and lengthening its cycling life.
An interpretation has been put forward of the fact that chloride ions have deleterious effects on... more An interpretation has been put forward of the fact that chloride ions have deleterious effects on the anodie passivation of AI, Fe, Cr and Fe-Cr alloys whereas some other metals such as Ti, Ta, Mo, W, and Zr do not lose their passivity on anodization in solutions containing chloride ions. The ideas put forward involve use of solid state concepts and considerations of coordination chemistry. It has been shown that high. metal-metal bond energies and high lattice energies of metal oxides are responsible for lesser tendency of metal ions of Ti, Ta, Mo, W and Zr to leave the lattice of the corresponding metal or metal-oxide, respectively. Further, even when their atoms or ions do find their way into the solution, they are irreversibly stabilized by the formation of stable complexes of "inner orbital" type, in terms of Taube's classification. Opposite considerations apply for the case of easily corroding metals such as AI, Fe, Cr and Fe-Cr alloys. Exceptionally easy tendency of aluminium to corrode on anodization in presence of a variety of anions has also been discussed in terms of the foregoing and other related concepts. A possible hypothetical scheme for the pitting corrosion of Al, Fe, etc., has also been mentioned. R6sum6-On avance une interpretation du fait que les ions de chlorure ont des effets delterioniques sur la passivit6 anodique de rAl, Fe, Cr et des alliages Fe-Cr, tandis que d'autres m6taux tels que le Ti, Ta, Mo, W et Zr gardent leur passivit6 devant des solutions anodisantes contenant des ions de chlorure. Leg th6ories avanc6es comprerment l'utilisation de concepts de semi-conduction et des considerations sur la chimie des coordinations. On a d6montr6 que les hautes 6nergies d6velopp~es par les combinaisons m6tal-m6tal et les ~nergies des oxydes m6talliques sont responsables d'une r~duction de la tendance des ions de ces m~taux h s'~happer. De plus, m~me lorsque leurs atomes ou leurs ions trouvent un passage dans la solution, ils sont irr6versiblement stabilis6s par la formation de complexes stables du type "orbite int6rieure", selon la classification de Taube. Des consid6rations oppos6es s'appliquent aux cas des m~taux facilement corrod6s tels que AI, Fe, Cr, ainsi que leg alliages Fe-Cr. On a 6tudi6 aussi la tendance tr~s prononc~e de l'aluminium ~ se corroder en anodisation en presence de divers anions sous forme des concepts precedents et autres. On mentionne aussi un syst~me th6orique possible pour la corrosion par points de ralumlnium, du fer, etc. Zusammenfassung-Es wird eine Erkl~rung dafiir gegeben, dab C1-die anodische Passivierung yon AI, Fe, Cr und FeCr-Legierungen behindert, wogegen einige andere Metalle wie Ti, Ta, Mo, W und Zr ihre anodische Passivierung in CI-haltigen L6sungen nicht verlieren. Als Grundlage dienen Vorstellungen iiber FestkOrper-und Koordinationschemie. Es wird gezeigt, dab starke Metall-Metall-Bindungen und hohe Gitterenergien der Metalle und Metalloxyde die geringere Neigung der Metallionen des Ti, Ta, Mo, W und Cr zum Austritt aus ihrem MetaU-oder Metalloxydgitter verursachem Auch wenn Ionen dieser Metalle in die L6sung iibertreten, werden sic durch die Bildung stabiler Innerer Orbitalkomplexe irreversibel stabilisiert, wobei die Darstellungsweise yon Taube angewendet v, ird. Entgegengesetzte 0berlegungen gelten fiir die CI-empfindlichen Metalle wie A1, Fe und Cr und FeCr-Legierungen. Die auBerordentlich hohe Tendenz des Aluminiums, bei anodischer Polarisation in Gegenwart einer Reihe yon Anionen zu korrodieren, kann mit den gleichea und fihnlichen Vorstellungen gedeutet werden. Eine Hypothese fiir den Ablauf der LochfraBkorrosion yon AI, Fe uses. wird angegeben.
Recent ideas of Fehlner and Mott on low-temperature oxidation, both thermal and anodic, are exami... more Recent ideas of Fehlner and Mott on low-temperature oxidation, both thermal and anodic, are examined with regard to the magnitudes of metal-metal and metal-oxygen bond strengths and their involvment in the interpretations of oxidation behavior of metals and semiconductors. It is pointed out that the magnitudes of bond strengths used by them appear to be inconsistent with the estimates of other workers based on well-established procedures. Some possible consequences of the reevaluated M-M and M-O bond strengths as regards the oxidation characteristics of metals are briefly mentioned. Also discussed is the influence of the estimated semiconductivity of anodization oxides on the subsequent anodic behavior of these metals.
There are many areas of chemistry that draw heavily upon and interact strongly with the correspon... more There are many areas of chemistry that draw heavily upon and interact strongly with the corresponding advances in physics and which, together, are called chemical physics. The more common examples of these areas are quantum chemistry, statistical thermodynamics, and the myriad forms of spectroscopy, etc. Similarly, there is one prominent field of physics, namely, solid-state physics, which has a profound influence on the development and progress of electrochemistry. The research endeavor on electrochemical problems which depend heavily upon the notions of solid-state physics for their proper elucidation is best grouped under electrochemical physics, in analogy with the chemical physics mentioned above.
The nature of factors that determine the electrochemical activities of metals for the M z÷ + ze-~... more The nature of factors that determine the electrochemical activities of metals for the M z÷ + ze-~ M reaction have been investigated. High activities of metals for this reaction are inversely related to their metal-metal bond energies and to their electrocatalytic activities for the hydrogen evolution reaction. The significance of these observations is discussed in relation to many other relevant factors, such as the electronic structure of metals, the ligand-field theory, the complex-forming affinities of metal ions, the activation energy for the exchange of water molecules from the first coordination sphere of the metal ions, the heat of hydration of M z÷ ions and the mechanism of pitting potentials of metals. Correlative trends that permit some generalizations regarding the electrochemical activities of metals for the M z÷ + ze-~ .-~ M reaction have been shown to exist and are discussed.
The adsorption of oxygen by phthalocyanines has been studied by temperature programmed desorption... more The adsorption of oxygen by phthalocyanines has been studied by temperature programmed desorption between-160 and 400°C. A desorption peak is observed at-140°C for copper yhthalocynnine and at-115°C for iron phthalocyanine. The assoriated activation energies of desorption are 7.5 and 9.8 kcal mole-' and these two peaks corrrspond to a first order kinetics of drsorption. These results constitute the first direct evidence on the lack of rupture of the bond beiween t\%-o oxygen atoms in the molecule adsorbed on phthalocyanines. Finally, an attempt is made IO rxaminr the mechanistic proposals on the electroreduction of oxygen on phthalocyanines in the light, of the present results.
Many materials of practical interest are either semiconducting or insulating in nature. One of th... more Many materials of practical interest are either semiconducting or insulating in nature. One of the most important quantities characterising these materials, therefore, is the energy bandgap. In the present article, procedures available for estimating the bandgaps of binary, inorganic materials from thermochemical and related data have been briefly reviewed with special emphasis on recent work.
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Papers by Ashok Vijh