Multivalent Sn species synergistically favours the CO2-into-HCOOH conversion

Although Sn-based catalysts have recently achieved considerable improvement in selective electro-catalyzing CO 2 into HCOOH, the role of various valence Sn species is not fully understood due to the complexity and uncertainty of their evolution during the reaction process. Here, inspired by the theoretical simulations that the concomitant multivalent Sn (Sn 0 , Sn 11 and Sn IV ) can significantly motivate the intrinsic activity of Sn-based catalyst, the Sn/SnO/SnO 2 nanosheets were proposed to experimentally verify the synergistic effect of multivalent Sn species on the CO 2 -into-HCOOH conversion. During CO 2 reduction reaction, the Sn/SnO/SnO 2 nanosheets, which are prepared by the sequential hydrothermal reaction, calcined crystallization and low-temperature H 2 treatment, exhibit a high FE HCOOH of 89.6% at −0.9 V RHE as well as a large cathodic current density. Systematic experimental and theoretical results corroborate that multivalent Sn species synergistically energize the CO 2 activation, the HCOO* adsorption, and the electron transfer, which make Sn/SnO/SnO 2 favour the conversion from CO 2 into HCOOH in both thermodynamics and kinetics. This proof-of-concept study establishes a relationship between the enhanced performance and the multivalent Sn species, and also provides a practicable and scalable avenue for rational engineering high-powered electrocatalysts.