In-Sn alloy core-shell nanoparticles: In-doped SnOx shell enables high stability and activity towards selective formate production from electrochemical reduction of CO2

In-doped tin oxide shell with InSn4 core is exergonic for CO2-to-formate, thus demonstrating a current density of 236 mA/cm2 and FE of 92% for formate production. [Display omitted] •Sn-In NPs were prepared by a facile, wet-chemical method.•An InSn4 intermetallic core and an amorphous In-doped tin oxide shell was confirmed by XRD, XPS and TEM.•Sn-In exhibit a current density of 236 mA cm−2 and a faradaic efficiency of 94% at −0.98 V towards CO2R to formate.•Operando XANES and Raman spectroscopy reveal that the In-doped tin oxide shell remains stable under CO2R condition.•DFT calculations indicate that the In-doped tin oxide results in the formation of oxygen vacancy and stabilized tin oxide. SnO2 has been recognized as excellent catalyst towards formate production from electrochemical CO2 reduction (CO2R). However, it is a great challenge to prepare SnO2 that is stable under the working condition of CO2R and the active center of the SnO2-based catalyst towards CO2R has been illusive. In this work, Sn-In alloy nanoparticles display an InSn4 intermetallic core and an amorphous In-doped tin oxide shell and a CO2-to-formate faradaic efficiency of 94% and a current density of 236 mA cm−2 was achieved at −0.98 V. Operando X-ray absorption and Raman spectroscopy reveal that the In-doped tin oxide shell remains stable under CO2R condition. Density functional theory calculations indicate that the In-doped tin oxide results in the formation of oxygen vacancy, stabilized tin oxide shell and exergonic pathway for CO2-to-formate, which might account for the high performance of the catalysts towards CO2R.