Steering CO2 Electroreduction Selectivity toward Ethylene or Ethanol by Phosphorus Doping in Confined CuOx Nanobowl Reactors

Abstract

Controlling the selectivity between ethylene and ethanol in CO2 electroreduction remains a challenge. Here, we report a dual-regulation strategy that combines hollow-bowl nanoconfinement with phosphorus doping in CuOx. The hollow nanospheres act as nanoreactors that enrich CO2 and key intermediates, while P doping progressively tunes the Cu+/Cu0 ratio and modulates the adsorption strength of reaction intermediates. As a result, the P doping level serves as a P-content-dependent selectivity regulator: at a low P/Cu ratio of 0.05, the catalyst favors ethylene with a Faradaic efficiency of 45%; at a high ratio of 0.30, the selectivity shifts to ethanol, reaching 35%. Operando spectroscopy supports the involvement of *OCCOH as a plausible branching intermediate and shows a stronger *OC2H5-related response at higher P content, consistent with the increased ethanol selectivity. The hollow cavity amplifies this effect by enhancing the local availability of CO2-derived intermediates and increasing CO coverage. Together, geometric confinement and electronic modulation enable P-content-dependent regulation of the product distribution between ethylene and ethanol during CO2 electroreduction.