Competition between CO 2 Reduction and H 2 Evolution on Transition-Metal Electrocatalysts

作者：Yin-Jia Zhang, Vijay A. Sethuraman, Ronald Michalsky, Andrew A. Peterson · 发表于：ACS Catalysis · 年份：2014 · DOI：10.1021/cs5012298 · 被引用次数：504 · 研究领域：Electrocatalysts for Energy Conversion、CO2 Reduction Techniques and Catalysts、Advanced battery technologies research

The well-known hydrogen evolution reaction (HER) volcano plot describes the relationship between H binding energy and the corresponding hydrogen evolution catalytic activity, which depends on the species of metal. Under CO 2 /CO reduction conditions or in cases where CO impurities enter electrodes, the catalyst may exist under a high coverage of coadsorbed CO. We present DFT calculations that suggest that coadsorbed CO during hydrogen evolution will weaken the binding strength between H and the catalyst surface. For metals on the right-hand side (too weak of hydrogen binding) this should lead to a suppression of the HER, as has been reported for metals such as Cu and Pt. However, for metals on the left-hand side of the volcano (too strong of hydrogen binding), this may actually enhance the kinetics of the hydrogen evolution reaction, although this effect will be countered by a decreased availability of sites for HER, which are blocked by CO. We performed experiments in Ar and CO 2 environments of two representative metals that bind CO on the far right- and left-hand side of the volcano, namely, Cu and Mo (respectively). On Cu, we find that the CO 2 environment suppresses HER, which is consistent with previous findings. However, on Mo we find that the CO 2 environment enhances HER in the kinetically active region. This helps to explain the outstanding performance of copper in CO 2 reduction and suggests that searches for high-selectivity CO 2 /CO reduction catalysts may benefi...