Tuning adsorption strength of CO2 and its intermediates on tin oxide-based electrocatalyst for efficient CO2 reduction towards carbonaceous products

Theoretical calculations prove that the Sn3O4 lowers the activation barrier of producing HCOOH benefitting from moderate adsorption energies of intermediates (HCOO* and *H) among SnO, SnO2 and Sn3O4. As a result, a faradic efficiency for carbonaceous products over 97.7 % at −0.9 VRHE is obtained on the Sn3O4 electrocatalyst. This combination of rigorous experimental and theoretical studies clearly elucidates the advantages of Sn3O4 and sheds light on the rational design of SnOx-based electrocatalysts with special electronic structure for efficient CO2RR utilizations. [Display omitted] •DFT calculations are performed to decipher the behaviors of SnO, SnO2 and Sn3O4 toward electroreduction of CO2.•Sn3O4 possesses the lowest activation barrier for the formation of HCOOH.•Flower-like Sn3O4 delivers a FEcarbonaceous of 97.7% and a partial current density of 16.6 mA/cm2 at −0.9 VRHE.•An onset overpotential of 190mV, the lowest reported thus far, is achieved on Sn3O4.•The up-shifted electronic structure of Sn3O4 plays an essential role for the boosted production of carbonaceous products. The catalytic performance of electrocatalyst on carbon dioxide reduction reaction (CO2RR) heavily depends on the adsorption strength of intermediates and electronic structure. For the first time, Sn3O4 is identified as the most effective electrocatalyst for CO2RR among SnOx-based materials towards carbonaceous products by density functional theory calculation and experimental work. An optimized adsorption strength of intermediates is achieved on Sn3O4 owing to the originally synergistic Sn2+ and Sn4+ effect resulted from the unique electronic structure of Sn3O4. Additionally, with an up-shifted band structure, Sn3O4 imparts the moderate adsorption energies of *H and HCOO* intermediate, which suppresses the hydrogen evolution reaction and promotes the intrinsic catalytic efficiency of CO2RR. The synthesized Sn3O4 electrocatalyst delivers a carbonaceous faradic efficiency of ∼97.7% with a partial current density of 16.6 mA/cm2 at −0.9 VRHE. The corresponding overpotential of 190 mV is lower than the values from most of the reported SnOx-based electrocatalysts.