Cu atomic clusters on N-doped porous carbon with tunable oxidation state for the highly-selective electroreduction of CO2

Efficient catalysts for the electrochemical CO2 reduction reaction (CO2RR) are highly required for solving the environmental crisis. However, the product selectivity and the catalyst durability for CO2RR are still big problems. Here, we synthesized ultra-small Cu atomic clusters (ACs) dispersed on an N-doped porous carbon (NPC) support (Cu ACs/NPC) for efficient and highly selective CO2RR to CO. The Cu ACs/NPC catalyst can achieve a maximum faradaic efficiency (FE) of 93.2% for CO production at a low potential of -0.5 V (vs. RHE), without any deactivation during 24 h of electrolysis. To the best of our knowledge, the Cu ACs/NPC catalyst, with high selectivity, low overpotential and excellent stability, represents one of the best Cu-based catalysts ever reported for CO2RR to CO. The favorable structure of the Cu ACs on the support means that they have large surface active sites to enhance CO2 adsorption for excellent performance. Moreover, in situ X-ray absorption spectroscopy (XAS) reveals that the Cu ACs/NPC has a tunable oxidation state, which can be easily switched between air-stable Cu2+ and highly reductive Cu-0 for efficient CO2RR. A combination of favorable structure and tunable oxidation state thus results in high activity towards the CO2RR.