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. It is important yet challenging to improve the interface contact between commonly used carbon conductive layer and metal oxide catalysts. Here the authors propose BiCuSeO with alternant active [Bi2O2](2+) sublayers and conductive [Cu2Se2](2-) sublayer within its superlattice as efficient catalyst for CO2 electroreduction to formate.

Automated summary

This study proposes a superlattice model with 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. The active [Bi2O2]2+ sublayers retain oxidation states during CO2 electroreduction due to rapid electron transfer through the conductive [Cu2Se2]2- sublayer. Theoretical calculations reveal high activity of the [Bi2O2]2+ sublayers, achieving over 90% formate selectivity. This work expands the understanding and improvement of CO2 electroreduction properties in metal oxide systems.