Interface engineering of a GaN/In2O3 heterostructure for highly efficient electrocatalytic CO2 reduction to formate

Electrocatalytic CO 2 reduction reaction (eCO 2 RR) to obtain formate is a promising method to consume CO 2 and alleviate the energy crisis. Indium-based electrocatalysts have demonstrated considerable potential to produce formate. However, their unsatisfactory long-term stability and selectivity restrict their widespread application. In this study, a heterostructure of GaN- and In 2 O 3 -encapsulated porous carbon nanofibers was constructed via electrospinning and the phase transition of eutectic gallium-indium during calcination . The GaN and In 2 O 3 nanoparticle-encapsulated porous carbon nanofibers, when used as electrocatalysts for eCO 2 RR, displayed high formate selectivity with a faradaic efficiency of 87% and maximum partial current density of 29.7 mA cm −2 in a 0.5 mol L −1 KHCO 3 aqueous solution. The existence of the interface can cause a positive shift in the In 3 d binding energy, leading to electronic redistribution. Moreover, the GaN component induced a higher proportion of O-vacancy sites in the In 2 O 3 phase, resulting in improved selectivity for CO 2 -to-formate. In-situ Raman experiments and density functional theory calculations revealed that the interface between GaN and In 2 O 3 could lower the adsorption energy of the key intermediates for formate production, thus providing superior eCO 2 RR performance. In addition, the framework of the porous carbon nanofibers exhibited a large electrochemically active surface area, which enabled the full exposure of the active sites. This study highlights the cooperation between GaN and In 2 O 3 components and provides new insights into the rational design of catalysts with high CO 2 -to-formate conversion efficiencies.