【摘要】 尽管许多催化剂已经被报道用于电化学转换二氧化碳（CO₂）到甲烷（CH₄）或者二碳（C₂）产物,然而目前对各种产物之间的关联的研究仍然不够深入,这阻碍着催化剂设计的进一步发展.本文通过研究商品化铜粉（Cu）作为CO₂电还原的阴极催化剂,发现一氧化碳中间体（*CO）在催化剂表面的覆盖度在较大的电位区间内会保持基本不变,且在这个电位区间内, CH₄与C₂产物的分电流密度呈线性关系,这一结论得到了理论动力学分析的支持.由于*CHO中间体分子是产生CH₄（*CHO→CH₄）与C₂产物（*CHO+*CO→C₂）的共同中间体,我们进一步猜想该线性关系是普遍存在的,且可以通过调节催化剂表面的吸附氢（*H）或者一氧化碳（*CO）的覆盖度,以分别促进CH₄或者C₂产物的生成,并改变线性关系的斜率.为了验证该猜想,本文合成了碳包覆的铜（Cu@C）催化剂,其中碳层可增加催化剂表面的*H覆盖度从而提高CH₄的产生,最高的CH₄法拉第效率(FE_CH4)达到52%,相应的分电流密度为±337 m A cm±2.另一方面,合成了银掺杂的铜催化剂,其中掺杂的银用以产生CO,以进一步提高催化剂表面的*CO覆盖度.该催化剂二氧化碳电还原的选择性变成了C₂产物为主,最高C₂产物的法拉第效率(FE_C2)达到79%,相应的分电流密度为±421 m A cm±2.不仅如此,在这两种催化剂上, CH₄与C₂产物的分电流密度仍然保持良好的线性关系.本文工作揭示了CH₄与C₂产物产率的线性关系,以及反应中间分子的调控策略,为电催化二氧化碳还原为不同的产物提供了参考.更多还原

【Abstract】 Although many catalysts have been reported for the CO₂ electroreduction to C₁ or C₂ chemicals, the insufficient understanding of fundamental correlations among different products still hinders the development of universal catalyst design strategies. Herein, we first discover that the surface *CO coverage is stable over a wide potential range and reveal a linear correlation between the partial current densities of CH₄ and C₂ products in this potential range, also supported by the theoretical kinetic analysis. Based on the mechanism that *CHO is the common intermediate in the formation of both CH₄（*CHO → CH4）and C₂（*CHO + *CO → C₂）, we then unravel that this linear correlation is universal and the slope can be varied by tuning the surface *H or *CO coverage to promote the selectivity of CH₄ or C₂ products,respectively. As proofs-of-concept, using carbon-coated Cu particles, the surface *H coverage can be increased to enhance CH₄ production, presenting a high CO₂-to-CH₄ Faradaic efficiency(FE_CH4～52%)and an outstanding CH₄ partial current density of –337 m A cm^-2. On the other hand, using an Agdoped Cu catalyst, the CO₂RR selectivity is switched to the C₂ pathway, with a substantially promoted FE_C2 of 79% and a high partial current density of –421 m A cm^-2. Our discovery of tuning intermediate coverages suggests a powerful catalyst design strategy for different CO₂ electroreduction pathways.更多还原