Nanoporous tin oxides for efficient electrochemical CO2 reduction to formate

CO2electroreduction reaction(CO2RR) has been considered as an effective technology to close the anthropogenic carbon cycle. Formate, a product of two-electron transfer in CO2RR, is an economically valuable feedstock. In this work, nanoporous tin oxides were controllable synthesized by a facile and scalable electrochemical anodic oxidation method. XPS result indicated that the increased Sn4+species after anodic oxidation were beneficial to reduce the overpotential of formate formation. Operando Raman spectra revealed that the enhanced formate selectivity could be attributed to the high local p H within the porous structure, which suppresses hydrogen evolution reaction(competing reaction against CO2RR). Further flow cell test showed a formate partial current density of 285 mA cm-2with the selectivity of 96.4%, indicating a promising industrial application prospect.