Electrocatalytic CO2 reduction (CO2RR) to valuable fuels is a promising approach to mitigate energy and environment problems, but controlling the reaction pathways and products remains challenging. Here, a novel Cu2O nanoparticle film is synthesized by square-wave (SW) electrochemical redox cycling of high purity Cu foils. The cathode afforded up to 98% Faradaic efficiency (FE) for CO2 electroreduction to nearly pure formate under ≧45 atm of CO2 in bicarbonate catholytes. When paired with a newly developed NiFe hydroxide-carbonate anode in KOH/borate anolyte, a two-electrode high-pressure electrolysis cell achieved a high energy conversion efficiency up to 55.8% stably for long-term formate production. While the high-pressure condition drastically increased the solubility of CO2 to enhance CO2RR and suppress hydrogen evolution, Cu2O (111) oriented film was found important to afford near ~100% CO2 reduction to formate. The results have implications to CO2 reduction into a single liquid product with high energy conversion efficiency.

中文翻译：

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铜基电催化剂在高压下电还原 CO2 以形成甲酸盐，具有高能量转换效率

将 CO2 电催化还原 (CO2RR) 还原为有价值的燃料是缓解能源和环境问题的一种很有前景的方法，但控制反应途径和产物仍然具有挑战性。在这里，通过高纯度铜箔的方波（SW）电化学氧化还原循环合成了一种新型的 Cu2O 纳米颗粒薄膜。阴极提供高达 98% 的法拉第效率 (FE)，用于在碳酸氢盐阴极电解液中在≥45 个大气压的 CO2 下将 CO2 电还原为几乎纯的甲酸盐。当与新开发的 KOH/硼酸盐阳极液中的 NiFe 氢氧化物-碳酸盐阳极配合使用时，双电极高压电解槽实现了高达 55.8% 的高能量转换效率，可长期稳定生产甲酸盐。虽然高压条件极大地增加了 CO2 的溶解度，以提高 CO2RR 并抑制析氢，发现 Cu2O (111) 取向膜对于提供接近约 100% 的 CO2 还原为甲酸盐很重要。结果对将 CO2 还原为具有高能量转换效率的单一液体产品具有重要意义。