Enabling durable selectivity of CO2 electroreduction to formate achieved by a multi-layer SnOx structure

In this study, a multi-layer SnOx structure was prepared by a ligand-confined growth strategy via the hydrothermal synthesis in the presence of n-butylamine and H2O. At an optimized proportion of n-butylamine and H2O (volume ratio of 1:1), the SnOx(1:1) catalyst exhibited a high formate Faradaic efficiency of 93.2% and remained durable over 40 h electrocatalysis at -1.15 V vs. RHE for at least 5 recycles. The multi-layer SnOx by means of reduction from Sn(IV) to Sn(II) species, which polarized CO2 and undergone a protoncoupled electron transfer to gain formate. Moreover, the specific multi-layer structure could stabilize the formation of Sn(II) species to achieve a highly stable selectivity of formate. With the loss of a relatively negative potential, the activated Sn(II) state was spontaneously oxidized to Sn(IV) species on the surface of catalyst. The effective reversibility of the Sn (II) and Sn(IV) species maintained the reproducibility for electrocatalytic CO2 reduction.