scholarly journals Fundamental Mechanistic Understanding of Electrocatalysis of Oxygen Reduction on Pt and Non-Pt Surfaces: Acid versus Alkaline Media

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Nagappan Ramaswamy ◽  
Sanjeev Mukerjee
Keyword(s):  
Electron Transfer ◽  
Oxygen Reduction ◽  
Active Site ◽  
Electrode Materials ◽  
Strong Dependence ◽  
Outer Sphere ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Wide Range ◽  
Inner Sphere

Complex electrochemical reactions such as Oxygen Reduction Reaction (ORR) involving multi-electron transfer is an electrocatalytic inner-sphere electron transfer process that exhibit strong dependence on the nature of the electrode surface. This criterion (along with required stability in acidic electrolytes) has largely limited ORR catalysts to the platinum-based surfaces. New evidence in alkaline media, discussed here, throws light on the involvement of surface-independent outer-sphere electron transfer component in the overall electrocatalytic process. This surface non-specificity gives rise to the possibility of using a wide-range of non-noble metal surfaces as electrode materials for ORR in alkaline media. However, this outer-sphere process predominantly leads only to peroxide intermediate as the final product. The importance of promoting the electrocatalytic inner-sphere electron transfer by facilitation of direct adsorption of molecular oxygen on the active site is emphasized by using pyrolyzed metal porphyrins as electrocatalysts. A comparison of ORR reaction mechanisms between acidic and alkaline conditions is elucidated here. The primary advantage of performing ORR in alkaline media is found to be the enhanced activation of the peroxide intermediate on the active site that enables the complete four-electron transfer. ORR reaction schemes involving both outer- and inner-sphere electron transfer mechanisms are proposed.

scholarly journals Cross Sphere Electrode Reaction: the Case of Hydroxyl Desorption during the Oxygen Reduction Reaction on Pt(111) in Alkaline Media

2021 ◽  
Author(s):  
Yuke Li ◽  
Zhi-Feng Liu
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Outer Sphere ◽  
Electrode Reaction ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Ab Initio Molecular Dynamics ◽  
Hydroxide Ion ◽  
Molecular Dynamics Calculations ◽  
Inner Sphere

Hydroxide ion is a common electrolyte when electrode reactions take place in alkaline media. In the case of oxygen reduction reaction on Pt(111), we demonstrate by ab initio molecular dynamics calculations, that the desorption of hydroxyl (OH*) from the electrode surface to form a solvated OH<sup>−</sup> is a cross sphere process, with the reactant OH* in the inner sphere and the product OH<sup>−</sup> directly generated in the aqueous outer sphere. Such a mechanism is distinct from the typical inner sphere and outer sphere reactions. It is dictated by the strong hydrogen bonding interactions between a hydroxide ion and water molecules and facilitated by proton transfer through solvation layers. It should play a significant role whenever OH* desorption, or its reverse, OH<sup>−</sup> adsorption, is involved in an electrochemical reaction

scholarly journals Cross Sphere Electrode Reaction: the Case of Hydroxyl Desorption during the Oxygen Reduction Reaction on Pt(111) in Alkaline Media

2021 ◽  
Author(s):  
Yuke Li ◽  
Zhi-Feng Liu
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Outer Sphere ◽  
Electrode Reaction ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Ab Initio Molecular Dynamics ◽  
Hydroxide Ion ◽  
Molecular Dynamics Calculations ◽  
Inner Sphere

Hydroxide ion is a common electrolyte when electrode reactions take place in alkaline media. In the case of oxygen reduction reaction on Pt(111), we demonstrate by ab initio molecular dynamics calculations, that the desorption of hydroxyl (OH*) from the electrode surface to form a solvated OH<sup>−</sup> is a cross sphere process, with the reactant OH* in the inner sphere and the product OH<sup>−</sup> directly generated in the aqueous outer sphere. Such a mechanism is distinct from the typical inner sphere and outer sphere reactions. It is dictated by the strong hydrogen bonding interactions between a hydroxide ion and water molecules and facilitated by proton transfer through solvation layers. It should play a significant role whenever OH* desorption, or its reverse, OH<sup>−</sup> adsorption, is involved in an electrochemical reaction

Inner Sphere Electron Transfer Promotion on Homogeneously Dispersed Fe-Nx Centers for Energy-Efficient Oxygen Reduction Reaction

2020 ◽  
Vol 12 (32) ◽  
pp. 36026-36039 ◽  
Author(s):  
Ravi Nandan ◽  
Hemam Rachna Devi ◽  
Ritesh Kumar ◽  
Abhishek Kumar Singh ◽  
Chandan Srivastava ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Energy Efficient ◽  
Reduction Reaction ◽  
Inner Sphere

scholarly journals Insights into the role of an Fe–N active site in the oxygen reduction reaction on carbon-supported supramolecular catalysts

RSC Advances ◽  
2020 ◽  
Vol 10 (15) ◽  
pp. 8709-8716
Author(s):  
Lin Gu ◽  
Yunyun Dong ◽  
Yan Zhang ◽  
Bo Wang ◽  
Qing Yuan ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Site ◽  
Active Sites ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Supramolecular Catalysts

The PPYTZ–Fe/C catalyst containing Fe–N active sites exhibited high ORR catalytic activity and stability in alkaline media with a four-electron pathway progress.

scholarly journals Computational Screening of Doped Graphene Electrodes for Alkaline CO2 Reduction

2021 ◽  
Vol 8 ◽  
Author(s):  
Anand M. Verma ◽  
Karoliina Honkala ◽  
Marko M. Melander
Keyword(s):  
Electron Transfer ◽  
Electrode Materials ◽  
Co2 Reduction ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Hydrogen Electrode ◽  
Computational Screening ◽  
Alkaline Conditions ◽  
Doped Graphene ◽  
Metal Doped

The electrocatalytic CO2 reduction reaction (CO2RR) is considered as one of the most promising approaches to synthesizing carbonaceous fuels and chemicals without utilizing fossil resources. However, current technologies are still in the early phase focusing primarily on identifying optimal electrode materials and reaction conditions. Doped graphene-based materials are among the best CO2RR electrocatalysts and in the present work we have performed a computational screening study to identify suitable graphene catalysts for CO2RR to CO under alkaline conditions. Several types of modified-graphene frameworks doped with metallic and non-metallic elements were considered. After establishing thermodynamically stable electrodes, the electrochemical CO2RR to CO is studied in the alkaline media. Both concerted proton-coupled electron transfer (PCET) and decoupled proton and electron transfer (ETPT) mechanisms were considered by developing and using a generalization of the computational hydrogen electrode approach. It is established that the CO2 electrosorption and associated charge transfer along the ETPT pathway are of utmost importance and significantly impact the electrochemical thermodynamics of CO2RR. Our study suggests an exceptional performance of metal-doped nitrogen-coordinated graphene electrodes, especially 3N-coordinated graphene electrodes.

scholarly journals Computational Screening of Doped Graphene Electrodes for Alkaline CO2 Reduction

2020 ◽  
Author(s):  
Anand Mohan Verma ◽  
Karoliina Honkala ◽  
Marko Melander
Keyword(s):  
Electron Transfer ◽  
Electrode Materials ◽  
Co2 Reduction ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Hydrogen Electrode ◽  
Computational Screening ◽  
Alkaline Conditions ◽  
Doped Graphene ◽  
Metal Doped

The electrocatalytic CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) is considered as one of the most promising approaches to synthesizing carbonaceous fuels and chemicals without utilizing fossil resources. However, current technologies are still in the early phase focusing primarily on identifying optimal electrode materials and reaction conditions. Doped graphene-based materials are among the best CO<sub>2</sub>RR electrocatalysts and in the present work we have performed a computational screening study to identify suitable graphene catalysts for CO<sub>2</sub>RR to CO under alkaline conditions. Several types of modified-graphene frameworks doped with metallic and non-metallic elements were considered. After establishing thermodynamically stable electrodes, the electrochemical CO<sub>2</sub>RR to CO is studied in the alkaline media. Both concerted proton-coupled electron transfer (PCET) and decoupled proton and electron transfer (ETPT) mechanisms were considered by developing and using a generalization of the computational hydrogen electrode approach. It is established that the CO<sub>2</sub> electrosorption and associated charge transfer along the ETPT pathway are of utmost importance and significantly impact the electrochemical thermodynamics of CO<sub>2</sub>RR. Our study suggests an exceptional performance of metal-doped nitrogen-coordinated graphene electrodes, especially 3N-coordinated graphene electrodes.

scholarly journals A Facile Method for the Generation of Fe3C Nanoparticle and Fe-Nx Active Site in Carbon Matrix to Achieve Good Oxygen Reduction Reaction Electrochemical Performances

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4779
Author(s):  
Yuzhe Wu ◽  
Yuntong Li ◽  
Conghui Yuan ◽  
Lizong Dai
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Site ◽  
High Performance ◽  
Electrode Materials ◽  
Carbon Materials ◽  
Carbon Matrix ◽  
Reduction Reaction ◽  
Electrochemical Performances ◽  
Active Electrode

Introduction of both nitrogen and transition metal elements into the carbon materials has demonstrated to be a promising strategy to construct highly active electrode materials for energy shortage. In this work, through the coordination reaction between Fe3+ and 1,3,5–tris(4–aminophenyl)benzene, metallosupramolecular polymer precursors are designed for the preparation of carbon flakes co-doped with both Fe and N elements. The as-prepared carbon flakes display wrinkled edges and comprise Fe3C nanoparticle and active site of Fe–Nx. These carbon materials exhibit excellent electrocatalytic performance. Towards oxygen reduction reaction (ORR), the optimized sample has Eonset and Ehalf-wave of 0.93 V and 0.83 V in alkaline system, respectively, which are very close to that of Pt/C. This approach may offer a new way to high performance and low-cost electrochemical catalysts.

scholarly journals Computational Screening of Doped Graphene Electrodes for Alkaline CO2 Reduction

2020 ◽  
Author(s):  
Anand Mohan Verma ◽  
Karoliina Honkala ◽  
Marko Melander
Keyword(s):  
Electron Transfer ◽  
Electrode Materials ◽  
Co2 Reduction ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Hydrogen Electrode ◽  
Computational Screening ◽  
Alkaline Conditions ◽  
Doped Graphene ◽  
Metal Doped

The electrocatalytic CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) is considered as one of the most promising approaches to synthesizing carbonaceous fuels and chemicals without utilizing fossil resources. However, current technologies are still in the early phase focusing primarily on identifying optimal electrode materials and reaction conditions. Doped graphene-based materials are among the best CO<sub>2</sub>RR electrocatalysts and in the present work we have performed a computational screening study to identify suitable graphene catalysts for CO<sub>2</sub>RR to CO under alkaline conditions. Several types of modified-graphene frameworks doped with metallic and non-metallic elements were considered. After establishing thermodynamically stable electrodes, the electrochemical CO<sub>2</sub>RR to CO is studied in the alkaline media. Both concerted proton-coupled electron transfer (PCET) and decoupled proton and electron transfer (ETPT) mechanisms were considered by developing and using a generalization of the computational hydrogen electrode approach. It is established that the CO<sub>2</sub> electrosorption and associated charge transfer along the ETPT pathway are of utmost importance and significantly impact the electrochemical thermodynamics of CO<sub>2</sub>RR. Our study suggests an exceptional performance of metal-doped nitrogen-coordinated graphene electrodes, especially 3N-coordinated graphene electrodes.

scholarly journals Synthesis of Ti4O7/Ti3O5 Dual-Phase Nanofibers with Coherent Interface for Oxygen Reduction Reaction Electrocatalysts

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3142
Author(s):  
Ruyue Shi ◽  
Ying Huang ◽  
Miaoran Li ◽  
Ying Zhu ◽  
Xuexia He ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Catalytic Performance ◽  
Reduction Reaction ◽  
Hydrothermal Growth ◽  
Alkaline Media ◽  
Dual Phase ◽  
Orientation Relationships ◽  
Methanol Tolerance

Electrocatalysts play an important role in oxygen reduction reaction (ORR) in promoting the reaction process. Although commercial Pt/C exhibits excellent performance in ORR, the low duration, high cost, and poor methanol tolerance seriously restrict its sustainable development and application. TinO2n−1 (3 ≤ n ≤ 10) is a series of titanium sub-oxide materials with excellent electrical conductivity, electrochemical activity, and stability, which have been widely applied in the field of energy storage and catalysis. Herein, we design and synthesize Ti4O7/Ti3O5 (T4/T3) dual-phase nanofibers with excellent ORR catalytic performance through hydrothermal growth, which is followed by a precisely controlled calcination process. The H2Ti3O7 precursor with uniform size can be first obtained by optimizing the hydrothermal growth parameters. By precisely controlling the amount of reducing agent, calcination temperature, and holding time, the T4/T3 dual-phase nanofibers with uniform morphology and coherent interfaces can be obtained. The orientation relationships between T4 and T3 are confirmed to be [ 001 ] T 3 / / [ 031 ] T 4 , ( 100 ) T 3 / / ( 92 6 ¯ ) T 4 , and ( 010 ) T 3 / / ( 1 2 ¯ 6 ) T 4 , respectively, based on comprehensive transmission electron microscopy (TEM) investigations. Furthermore, such dual-phase nanofibers exhibit the onset potential and half-wave potential of 0.90 V and 0.75 V as the ORR electrocatalysts in alkaline media, respectively, which illustrates the excellent ORR catalytic performance. The rotating ring-disk electrode (RRDE) experiment confirmed the electron transfer number of 3.0 for such catalysts, which indicates a mixture of two electron and four electron transfer reaction pathways. Moreover, the methanol tolerance and cycling stability of the catalysts are also investigated accordingly.

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