Active and conductive layer stacked superlattices for highly selective CO₂ electroreduction

Metal oxides are archetypal CO₂ reduction reaction electrocatalysts, yet inevitable self-reduction will enhance competitive hydrogen evolution and lower the CO₂ electroreduction selectivity. Herein, we propose a tangible superlattice model of alternating metal oxides and selenide sublayers in which electrons are rapidly exported through the conductive metal selenide layer to protect the active oxide layer from self-reduction. Taking BiCuSeO superlattices as a proof-of-concept, a comprehensive characterization reveals that the active [Bi₂O₂]²⁺ sublayers retain oxidation states rather than their self-reduced Bi metal during CO₂ electroreduction because of the rapid electron transfer through the conductive [Cu₂Se₂]^2- sublayer. Theoretical calculations uncover the high activity over [Bi₂O₂]²⁺ sublayers due to the overlaps between the Bi p orbitals and O p orbitals in the OCHO* intermediate, thus achieving over 90% formate selectivity in a wide potential range from -0.4 to -1.1 V. This work broadens the studying and improving of the CO₂ electroreduction properties of metal oxide systems.