Facet Dependence of CO2 Reduction Paths on Cu Electrodes,ACS Catalysis

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Facet Dependence of CO2 Reduction Paths on Cu Electrodes
ACS Catalysis ( IF 11.3 ) Pub Date : 2015-12-08 00:00:00 , DOI: 10.1021/acscatal.5b01967
Wenjia Luo ₁ , Xiaowa Nie ₂ , Michael J. Janik ₃ , Aravind Asthagiri ₁

Affiliation

Experimental results have shown that CO₂ electroreduction is sensitive to the surface morphology of Cu electrodes. We used density functional theory (DFT) to evaluate the thermodynamics and kinetics of CO₂ reduction pathways on Cu(100) and Cu(111) with the aim of understanding the experimentally reported differences in CO₂ reduction products. Results suggest that the hydrogenation of CO* to hydroxymethylidyne (COH*) or formyl (CHO*) is a key selective step. Cu(111) favors COH* formation, through which methane and ethylene are produced via a common CH₂ species under high overpotential (<−0.8 V vs RHE). On Cu(100), formation of CHO* is preferred and ethylene formation goes through C–C coupling of two CHO* species followed by a series of reduction steps of the C₂ intermediates, under relatively lower overpotential (−0.4 to −0.6 V vs RHE). Further reduction of these C₂ intermediates, however, require larger potentials (∼−1.0 V vs RHE) and conflicts with the experimentally observed low potential pathway to C₂ products on Cu(100). Calculations show that the presence of (111) step sites on the flat (100) terrace can reduce the overpotential for C₂ production on the Cu electrode, which may be present on Cu(100) due to reconstruction. On Cu(100), a change in CO* coverage from low to high with increasing negative applied potential can trigger a switch from ethylene/ethanol to methane/ethylene as the reduction products by affecting the relative stability of CHO* and COH*.

中文翻译：

Cu电极上CO ₂还原路径的切面依赖性

实验结果表明，CO ₂电还原对Cu电极的表面形态敏感。我们使用密度泛函理论（DFT）评估了Cu（100）和Cu（111）上CO ₂还原途径的热力学和动力学，目的是了解实验报告的CO ₂还原产物的差异。结果表明，将CO *氢化为羟甲基二炔（COH *）或甲酰基（CHO *）是关键的选择性步骤。Cu（111）促进COH *的形成，通过共同的CH ₂生成甲烷和乙烯高电位（<-0.8 V vs RHE）下的其他物种。在Cu（100）上，首选形成CHO *，并且乙烯形成通过两个CHO *物种的C–C偶联，然后在相对较低的过电势（-0.4至-0.6 V）下进行一系列C ₂中间体的还原步骤与RHE）。然而，进一步还原这些C ₂中间体需要更大的电势（相对于RHE约为-1.0 V），并且与实验观察到的向Cu（100）上C ₂产物的低电势通路相冲突。计算表明，在平坦的（100）平台上存在（111）阶跃点可以减少C ₂的超电势在铜电极上产生的铜，由于重建可能会存在于铜（100）上。在Cu（100）上，随着负施加电位的增加，CO *覆盖率从低到高的变化会通过影响CHO *和COH *的相对稳定性而触发乙烯/乙醇向甲烷/乙烯作为还原产物的转换。

更新日期：2015-12-08

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