Spatiotemporal active phase evolution for CO2 electrocatalysis

Revealing and redirecting the dynamic evolution of active species in efficient electrochemical CO₂ reduction (ECR) catalystsis challenging. By observing the chemical and morphological evolution in highly efficient ECR catalysts at the nanoscale via operando soft X-ray microscopy, we identified the dynamic transformation of cationic Cu species during operation. The surface Cu²⁺ phases, observed during a dynamic phase transformation of Cu(OH)2, additionally boost C–C coupling activity beyond the capability of metallic Cu phases. We suggest that copper(II)-carbonate-hydroxide species could dynamically persist under a cathodic environment. By observing the Cu⁺ phase during the phase transformation and the formation of surface Cu²⁺ species, we were able to electrochemically redirect low-active catalysts into high-active catalysts for C-C coupling. Density functional theory calculations also support that Cu²⁺ species could contribute to C–C coupling activity enhancement via *CO adsorption energy modulation.

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