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.