scholarly journals Electrokinetic and in situ spectroscopic investigations of CO electrochemical reduction on copper

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jing Li ◽  
Xiaoxia Chang ◽  
Haochen Zhang ◽  
Arnav S. Malkani ◽  
Mu-jeng Cheng ◽  
...  
Keyword(s):  
Mass Transport ◽  
Active Sites ◽  
Gas Diffusion ◽  
Reduction Reaction ◽  
Adsorbed Hydrogen ◽  
Diffusion Type ◽  
Proton Coupled Electron Transfer ◽  
Alkaline Electrolytes ◽  
Reaction Orders

AbstractRigorous electrokinetic results are key to understanding the reaction mechanisms in the electrochemical CO reduction reaction (CORR), however, most reported results are compromised by the CO mass transport limitation. In this work, we determined mass transport-free CORR kinetics by employing a gas-diffusion type electrode and identified dependence of catalyst surface speciation on the electrolyte pH using in-situ surface enhanced vibrational spectroscopies. Based on the measured Tafel slopes and reaction orders, we demonstrate that the formation rates of C2+ products are most likely limited by the dimerization of CO adsorbate. CH4 production is limited by the CO hydrogenation step via a proton coupled electron transfer and a chemical hydrogenation step of CO by adsorbed hydrogen atom in weakly (7 < pH < 11) and strongly (pH > 11) alkaline electrolytes, respectively. Further, CH4 and C2+ products are likely formed on distinct types of active sites.

Gas Diffusion-Type Oxygen Electrode Using Perovskite-Type Oxides for Metal-Air Batteries

1995 ◽  
Vol 393 ◽  
Author(s):  
Takeo Hyodo ◽  
Norio Miura ◽  
Noboru Yamazoe
Keyword(s):  
Active Sites ◽  
Electrode Reaction ◽  
Oxygen Electrode ◽  
Gas Diffusion ◽  
Air Cathode ◽  
Diffusion Type ◽  
Reduction Behavior ◽  
Term Operation ◽  
Electron Reduction ◽  
Perovskite Type

ABSTRACTIn order to develop an air cathode of metal-air batteries, oxygen reduction behavior of gas diffusion-type carbon electrodes loaded with perovskite-type oxides, Lai-xA'xFe03(A'=Ca, Sr, Ba, 0<x<1.0), was examined in 8 M KOH at 60 °C. Among the oxide catalysts tested, La0.5Sr0.5Fe03(specific surface area : 21.5 m2.g−1) gave the highest electrode performance. On the basis of electrode reaction kinetics, H2O2decomposition rates, and temperature programed desorption of oxygen, it was concluded that such a performance was attributable to the active sites of the oxide for the direct 4-electron reduction of oxygen. Moreover, the electrode using Lao.5Sro.5FeO3was found to be rather stable in a short-term operation for 90 h at 300 mA-cm−2.

An MOF-derived C@NiO@Ni electrocatalyst for N2 conversion to NH3 in alkaline electrolytes

2020 ◽  
Vol 4 (1) ◽  
pp. 164-170 ◽  
Author(s):  
Shijian Luo ◽  
Xiaoman Li ◽  
Wanguo Gao ◽  
Haiqiang Zhang ◽  
Min Luo
Keyword(s):  
Active Sites ◽  
Oxygen Vacancies ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Alkaline Electrolytes

MOF-derived C@NiO@Ni are proposed as an efficient electrocatalyst for N2 reduction reaction in alkaline media. Abundant oxygen vacancies and NiO/Ni interfaces can act as active sites for adsorbing nitrogen and proton, respectively.

scholarly journals How Stable Are 2H-MoS2 Edges Under Hydrogen Evolution Reaction Conditions?

2021 ◽  
Author(s):  
Nawras Abidi ◽  
Audrey Bonduelle-Skrzypczak ◽  
Stephan Steinmann
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Active Sites ◽  
Density Functional ◽  
External Source ◽  
Operating Conditions ◽  
Adsorbed Hydrogen ◽  
Functional Theory ◽  
Acidic Conditions

MoS<sub>2</sub>, have emerged as a promising class of electrocatalysts for the production of H<sub>2</sub> via the hydrogen evolution reaction (HER) in acidic conditions.<div>The edges of MoS<sub>2</sub> are known for their HER activity, but their precise atomistic nature and stability under HER conditions is not yet known. In contrast to other typical uses of MoS<sub>2</sub> as a catalyst, under HER there is no external source of sulfur. Therefore, the sulfidation of the edges can only decrease under operating conditions and the thermodynamics of the process are somewhat ill-defined. Our results suggest that the 50%S S-edge may be active for HER via the Volmer-Tafel mechanism and is, despite a high H coverage, stable with respect to H<sub>2</sub>S release. </div><div>At the 50%S Mo-edge, the adsorbed hydrogen opens the way for H<sub>2</sub>S release, leading to the 0%S Mo-edge, which was previously investigated and found to be HER active. HER being a water-based process, we also considered the effect of the presence of H<sub>2</sub>O and the in-situ formation of OH. For the 50%S Mo-edge, H<sub>2</sub>O is only very weakly adsorbed and OH formation is unfavorable. Nevertheless, OH assists the loss of sulfur coverage, leading to OH-based HER active sites. In contrast, OH is strongly adsorbed on the 50%S S-edge. By explicitly considering the electrochemical potential using grand-canonical density functional theory, we unveil that the Volmer-Heyrovsky mechanism on sulfur sites is still accessible in the presence of surface OH at the 50%S S-edge. However, the 50%S S-edge is found to be mildly unstable with respect to H<sub>2</sub>S in the presence of water/OH. Hence, we suggest that the 50%S S-edge evolves over time towards a 0%S S-edge, covered by surface OH that will block permanently the active sites. </div>

Preparation of monodisperse ferrous nanoparticles embedded in carbon aerogels via in situ solid phase polymerization for electrocatalytic oxygen reduction

Nanoscale ◽  
2020 ◽  
Vol 12 (28) ◽  
pp. 15318-15324
Author(s):  
Wei Hong ◽  
Xin Feng ◽  
Lianqiao Tan ◽  
Aiming Guo ◽  
Bing Lu ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Solid Phase ◽  
Reduction Reaction ◽  
Carbon Aerogels ◽  
Structured Materials ◽  
Nitrogen Doped ◽  
Electrocatalytic Oxygen Reduction ◽  
Nitrogen Doped Carbon

Core–shell structured materials constructed by using Fe/Fe3C cores and nitrogen doped carbon shells represent a type of promising non-precious oxygen reduction reaction (ORR) catalyst due to well-established active sites at the interface positions.

In situ exsolved Co components on wood ear-derived porous carbon for catalyzing oxygen reduction over a wide pH range

2021 ◽  
Author(s):  
Yu Xu ◽  
Haiyan Zhang ◽  
Ping Zhang ◽  
Min Lu ◽  
Xiaoji Xie ◽  
...  
Keyword(s):  
Transition Metal ◽  
Oxygen Reduction ◽  
Porous Carbon ◽  
Active Sites ◽  
Reduction Reaction ◽  
Great Promise ◽  
Wide Ph Range ◽  
Ph Range ◽  
Carbon Catalysts

Carbon-based catalysts with transition metal active sites hold great promise for electrochemically catalyzing oxygen reduction reaction (ORR). However, it is still challenging to fabricate carbon catalysts containing transition metal active...

scholarly journals Testing a Silver Nanowire Catalyst for the Selective CO2 Reduction in a Gas Diffusion Electrode Half-cell Setup Enabling High Mass Transport Conditions

2019 ◽  
Vol 73 (11) ◽  
pp. 922-927 ◽  
Author(s):  
María de Jesús Gálvez-Vázquez ◽  
Shima Alinejad ◽  
Huifang Hu ◽  
Yuhui Hou ◽  
Pavel Moreno-García ◽  
...  
Keyword(s):  
Mass Transport ◽  
Co2 Reduction ◽  
Reaction Rates ◽  
Gas Diffusion ◽  
Reduction Reaction ◽  
Liquid Electrolyte ◽  
Gas Diffusion Electrode ◽  
Silver Nanowire ◽  
High Mass ◽  
Half Cell

In this work, we discuss the application of a gas diffusion electrode (GDE) setup for benchmarking electrocatalysts for the reductive conversion of CO2 (CO2 RR: CO2 reduction reaction). Applying a silver nanowire (Ag-NW) based catalyst, it is demonstrated that in the GDE setup conditions can be reached, which are relevant for the industrial conversion of CO2 to CO. This reaction is part of the so-called 'Rheticus' process that uses the CO for the subsequent production of butanol and hexanol based on a fermentation approach. In contrast to conventional half-cell measurements using a liquid electrolyte, in the GDE setup CO2 RR current densities comparable to technical cells (>100 mA cm–2) are reached without suffering from mass transport limitations of the CO2 reactant gas. The results are of particular importance for designing CO2 RR catalysts exhibiting high faradaic efficiencies towards CO at technological reaction rates.

scholarly journals Recent Advances in the Catalyst Design and Mass Transport Control for the Electrochemical Reduction of Carbon Dioxide to Formate

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 859 ◽  
Author(s):  
Muhammad Alfath ◽  
Chan Woo Lee
Keyword(s):  
Mass Transport ◽  
Electrochemical Reduction ◽  
Active Sites ◽  
Co2 Reduction ◽  
Aqueous Solubility ◽  
Reduction Reaction ◽  
Catalyst Design ◽  
Catalyst Composition ◽  
Reduction Of Co2 ◽  
Formate Production

Closing the carbon cycle by the electrochemical reduction of CO2 to formic acid and other high-value chemicals is a promising strategy to mitigate rapid climate change. The main barriers to commercializing a CO2 reduction reaction (CO2RR) system for formate production are the chemical inertness, low aqueous solubility, and slow mass transport characteristics of CO2, along with the low selectivity and high overpotential observed in formate production via CO2 reduction. To address those problems, we first explain the possible reaction mechanisms of CO2RRs to formate, and then we present and discuss several strategies to overcome the barriers to commercialization. The electronic structure of the catalyst can be tuned to favor a specific intermediate by adjusting the catalyst composition and tailoring the facets, edges, and corners of the catalyst to better expose the active sites, which has primarily led to increased catalytic activity and selectivity. Controlling the local pH, employing a high-pressure reactor, and using systems with three-phase boundaries can tune the mass transport properties of reactants at the catalyst surface. The reported electrocatalytic performances are summarized afterward to provide insight into which strategies have critical effects on the production of formate.

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