Phase engineering of Cu@Cu2O core-shell nanospheres for boosting tandem electrochemical CO2 reduction to C2+ products

Cu-based CO2 electrochemical reduction (CO2ER) is promising for reducing greenhouse gas emission and producing high-value multicarbon (C2+) chemicals and fuels. Unfortunately, the C2+ selectivity is still quite low. In this work, well-defined [email protected]2O core–shell nanospheres with time-dependent evolution of phase composition, crystallinity and morphology were specifically designed by a facile chemically induced self-transformation strategy. A maximum C2+ Faradaic efficiency (FE) exceeding 79%, including FEC2H4 reaching 44%, was achieved using phase-engineered [email protected]2O nanospheres. Based on the temperature-programmed desorption analyses and in-situ Raman spectroscopy, the adsorption behaviors of both CO2 reactant and *CO intermediate can be synergistically tuned by phase engineering of [email protected]2O nanospheres: Cu2O shell enhances *CO2 and *CO adsorption coverage, while porous Cu core concentrate and strengthens *CO intermediates for subsequent CO-CO coupling towards C2+ products. This work will shed new light on the phase engineering of Cu-based tandem electrocatalysts for tuning CO2/CO-catalyst interaction and modulating CO2ER processes and selectivity.