3D hierarchical porous indium catalyst for highly efficient electroreduction of CO2

The electrochemical reduction of CO2 requires highly active, selective as well as stable electrocatalysts. Herein, we report a three-dimensional hierarchical porous indium catalyst for the electroreduction of CO2 to formate. In aqueous bicarbonate solution, the catalyst exhibits a high faradaic efficiency for formate (approximate to 90%) in the potential range of -1.0 to -1.2 V (vs. reversible hydrogen electrode) and reaches an unprecedented formate production rate of 1.14 mmol cm(-2) h(-1) at -1.2 V. Additionally, the catalyst also displays a long-term stability (24 h). Density functional theory calculations reveal the catalytically selective nature of In for formate production. Independent of the crystal facet, In surfaces stabilise *OCHO, a key intermediate for the formate pathway, much more effectively than the *H (for the H-2 pathway) and *COOH (for the CO pathway) intermediates. Experimental results demonstrate that the improved CO2 reduction selectivity on the porous In catalyst originates from the reduced evolution of H-2, which is induced by the high local pH in the vicinity of the electrode. Furthermore, the porous In can also serve as a template to synthesise a porous Pd-In catalyst for tuning the selectivity of formate and CO, demonstrating its promising potential for CO2 electroreduction.