The electrocatalytic CO₂ reduction reaction (eCO₂RR) has been gaining increasing attention owing to its potential to contribute to sustainability in our society, although enhanced catalytic performance is a prerequisite for its implementation. Herein, Cu electrocatalysts modified with sulfur proved to selectively produce formate via aqueous eCO₂RR and thus to unexpectedly prevent the mechanistic fingerprint of Cu (i.e., the CO path). Initially, sulfur-modified copper catalysts (Cu–S) were prepared by the in situ reductive reconstruction of nano CuS precursors, revealing a positive correlation between particle size and selectivity toward formate. Subsequent studies over targeted submicron Cu–S particles with varying sulfur content demonstrated their evolution under reaction conditions, attaining a similar surface state comprising metallic Cu and sulfide phases, irrespective of the initial structure of the materials. In accordance, the initial sulfur content showed only a very limited influence on the catalytic performance, which remained at approximately 80% Faradaic efficiency toward formate at −0.8 V vs RHE, outperforming all cost-effective, earth-abundant, and nontoxic electrocatalysts reported to date for the production of formate via the aqueous eCO₂RR.

中文翻译：

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硫修饰的铜催化剂，用于电化学还原二氧化碳形成甲酸酯

尽管增强的催化性能是其实施的先决条件，但由于电催化的CO ₂还原反应（eCO ₂ RR）具有促进我们社会可持续发展的潜力，因此受到越来越多的关注。此处，事实证明，用硫改性的铜电催化剂可以通过eCO ₂水溶液选择性地生成甲酸。RR从而意外地防止了Cu的机械指纹（即CO路径）。最初，通过纳米CuS前体的原位还原重建制备了硫改性的铜催化剂（Cu-S），揭示了粒径与对甲酸酯的选择性之间呈正相关。随后针对具有不同硫含量的目标亚微米Cu-S颗粒进行的研究表明，它们在反应条件下的演变，获得了相似的表面状态，包括金属Cu和硫化物相，而不论材料的初始结构如何。因此，初始硫含量仅对催化性能产生非常有限的影响，在相对于RHE的-0.8 V时，对甲酸的法拉第效率保持在约80％法拉第效率，胜过所有具有成本效益的，富地球的₂ RR。