Gallium-indium bimetal sites in the indium-gallium metal organic framework for efficient electrocatalytic reduction of carbon dioxide into formate

In-based catalysts offer an attractive approach for electrocatalytic reduction of CO2 (eCO2RR) into formate. However, precisely controlling the adsorption of competitive intermediates (*COOH and *OCHO) on In-based catalysts remains a tremendous challenge. Based on that, Ga is introduced for optimizing the electronic structure of In and adsorption of competitive intermediates. Here the indium-gallium metal organic framework (InGaMOF) with rich In-Ga bimetal sites is synthesized by a simple two-step method. The best InGaMOF(5 : 1) catalyst exhibits an excellent formate faradaic efficiency of 93% at -0.5 V (vs. RHE). The structure-activity relationship is revealed by in situ electrochemical Fourier transform infrared spectroscopy and other techniques. The characterization data indicate that the generated In-Ga bimetal sites in InGaMOF(5 : 1) provide co-adsorbed sites for CO2 molecules, facilitating their initial adsorption and activation into *CO2-. Moreover, the atomic bridging of Ga with In atoms efficiently optimizes the electronic structure of In, which results in weaker In-C hybridization of competitive *COOH (for CO) and stronger In-O hybridization of *OCHO (for formate). This study provides a new insight for understanding the important role of Ga in Ga-based bimetal electrocatalysts towards the eCO2RR. In-Ga bimetal sites facilitate the initial adsorption and activation to *CO2- and adjust the surface electronic features, thus significantly promoting the favorable conversion of the adsorbed *OCHO intermediate toward formate.