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

Abstract

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.