Operando Reconstruction of CuO/SnO2 Nanosheets Promotes the Syngas Production from the Electrochemical CO2 Reduction Reaction

Electrochemically reducing CO2 (CO2RR) to high-value chemical products is recognized as a promising route to simultaneously reduce the consumption of fossil fuels and carbon emission. The fabrication of syngas with an appropriate H2/CO ratio by CO2RR has been widely studied, but the dynamic evolution of the catalyst is still ambiguous. Herein, the reconstruction of CuO/SnO2 nanosheets (NSs) with a heterojunction structure in the CO2RR process was reported by an in situ X-ray diffractometer technique. The products of the CO2RR on the optimized CuO/SnO2 NSs are CO and H2, achieving a nearly 100% total Faraday efficiency. Moreover, the resulting syngas is maintained at a constant 2:1 ratio of H2/CO over a wide potential of -0.8 to -1.2 V versus the reversible hydrogen electrode. Importantly, the detailed characterizations show that Cu2+ is reduced to Cu during the CO2RR process, while the valence state of Sn remains stable. This study presents strong experimental support for the dynamic evolution process of electrocatalysts in other energy conversion fields.