Active and conductive layer stacked superlattices for highly selective CO electroreduction.

Metal oxides are archetypal CO reduction reaction electrocatalysts, yet inevitable self-reduction will enhance competitive hydrogen evolution and lower the CO 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 [BiO] sublayers retain oxidation states rather than their self-reduced Bi metal during CO electroreduction because of the rapid electron transfer through the conductive [CuSe] sublayer. Theoretical calculations uncover the high activity over [BiO] 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 CO electroreduction properties of metal oxide systems.