Tailoring the electrolyte microenvironment of indium catalysts for enhanced formic acid electrosynthesis

Electrocatalytic carbon dioxide reduction reaction (CO 2 RR) to formic acid is considered an economically viable avenue toward carbon neutrality. Indium-based catalysts have garnered considerable attention in CO 2 RR owing to their elevated hydrogen evolution reaction (HER) overpotential and eco-friendly characteristics. We have synthesized In 2 O 3 nanofibers rich in oxygen vacancies using the electrospinning technique. The resultant 500-In 2 O 3 exhibited superior performance in converting CO 2 RR to HCOOH, achieving an impressive formate Faradaic efficiency (FE) of 92.1% at a current density of −600 mA cm −2 . Moreover, it demonstrated remarkable stability, maintaining its performance over 100 h at a current density of −300 mA cm −2 under a neutral electrolyte. Density functional theory (DFT) calculations, in conjunction with spectroscopic characterizations, have revealed that a Cl-modified In catalyst exhibits a lowered energy barrier for the formation of *HCOOH, while simultaneously inhibiting the generation of *H, in contrast to its pristine In counterpart. Ultimately, we successfully engineered a dual-electrode system capable of simultaneously producing formate at both the cathode and the anode. At a current density of −100 mA cm −2 , our system achieves a reduction in energy consumption by 12.5% and a significant enhancement in electrical energy conversion efficiency by 39.9%.