Highly stability Cu+ species in hollow Cu2O nanoreactors by modulating cavity size for CO2 electroreduction to C2+ products

In Cu-based electrocatalysts, appropriate amount of Cu0 and high concentration of Cu+ are essential for the efficient conversion of CO2 into C2+ products. An obstacle of CO2 electroreduction is the inevitable reduction of Cu+ to Cu0 at cathodic potential. Intermediates confinement is a promising solution to delay Cu+ deterioration, in which it is crucial to maintain an appropriate amount of Cu0 and Cu+ species to produce sufficient intermediates to protect most Cu+ species. Herein, based on the influence of Cu+/Cu0 ratio on the reaction process and its feedback, a series of hollow Cu2O nanoreactors with different cavity sizes were synthesized to modulate the concentration of intermediates and the coverage degree of Cu+, so as to realize a constant high Cu+/Cu0 ratio. The optimized hollow Cu2O nanoreactors achieved a C2+ Faradaic efficiency of 70.1 ± 0.2 % at a partial current density of −9.3 ± 0.1 mA cm−2 over 30 h and a large C2+-to-C1 ratio of 9.73. Operando Raman spectra and quasi in-situ Auger electron spectra confirmed that the moderate cavity Cu2O nanoreactors led to a full coverage of Cu+ and an optimal Cu+/Cu0 ratio of 8.12:1, which brought the stability of Cu+ species and cavity structure, as well as the enhanced CC dimerization.