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

Abstract

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 Cu⁰ for efficient CO₂RR. A combination of favorable structure and tunable oxidation state thus results in high activity towards the CO₂RR.