Active/Conductive Layer Stacked Superlattices for Highly Selective CO2 Electroreduction

Metal oxides are the archetypal CO2 reduction reaction (CO2RR) electrocatalysts, yet the inevitable self-reduction will enhance competitive hydrogen evolution and lower the CO2RR selectivity. Herein, we propose a tangible superlattice model of alternating metal oxide and sulfide sublayer in which electrons are rapidly exported through the conductive metal sulfide 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 their self-reduced Bi metal during CO2RR because of the rapid electron transfer through the conductive [Cu2Se2]2− sublayer. Theoretical ccalculations uncover the high activity over [Bi2O2]2+ sublayers due to the overlaps between the Bi p orbitals and O p orbitals in HCOO* intermediate, thus achieving over 90% formate selectivity in a wide potential range from − 0.4 to -1.1 V. This work broadens the horizons of studying and improving the CO2 electroreduction properties of metal oxide systems.