Pore-structure-enhanced electrochemical reduction of CO2 to formate on Sn-based double-layer catalysts

Sn-based materials can be used as electrocatalysts for the CO2 electroreduction reaction (CO2RR), preferentially producing formate. Although some Sn-based catalysts with a high faradaic efficiency for formate have been reported, the sensitivity of CO2RR activity to the catalyst structure remains elusive. Herein, a correlation between CO2RR activity and the geometric configuration of Sn-based catalysts was discovered using both double-shell SnOx nanospheres with apertures of different sizes, and CO2RR simulations using a three-step mechanism model. The kinetics analysis and simulation results suggest that a high loading of intermediate CO2,ads is the key to achieving high CO2RR performance with production of formate in the potential range -0.89 V similar to -1.26 V (vs. RHE). This understanding led to the design of double-shell SnOx nanospheres with enclosed apertures to increase the mesoporosity of the structure and hence its CO2 adsorption capability. Such a mechanism-guided approach to the design of catalysts not only enables a deep understanding of the CO2RR kinetics, but also sets a clear direction for the design of catalysts for scaled CO2RR applications.