Ordered Mesoporous Electrocatalysts for Highly Selective Formate Production from Electrocatalytic CO2 Reduction

Abstract

Ordered mesoporous materials offer significant advantages in reducing energy barriers, tuning intrinsic reaction pathways, and suppressing undesirable side reactions in electrocatalytic CO2 reduction reactions (CO2RR). Here, we present a straightforward method for the direct electrodeposition of ordered mesoporous CO2RR catalysts on a carbon-based porous transport layer, utilizing lyotropic liquid crystals (LLCs) as templates. The versatility of this method was demonstrated with tin-, bismuth-, and indium-based catalysts, all exhibiting pore sizes on the order of several nanometers. These ordered mesoporous catalysts efficiently and selectively drive CO2RR toward the value-added product of formate. They achieve partial current densities that are 3 to 8 times higher than those of disordered mesoporous reference samples, with a Faradaic efficiency (FE) of up to 93% at an optimal potential of -0.9 V vs. RHE. In a flow cell configuration, Sn-based catalysts deliver a current density of ~200 mA cm-2 over 22 hours at a potential of only -0.65 V vs. RHE. Spectroscopic and electrochemical analyses suggest that the high performance can be attributed to the exclusive exposure of active sites for the formate, improved mass transport, and modulated local microenvironments. Our work demonstrates a simple yet effective method for the direct deposition of efficient and selective catalysts onto electrodes. The insights gained from the underlying mechanisms provide valuable guidance for the design of high-performance CO2RR electrocatalysts.