Enhanced Electrochemical CO2 Reduction to Formate over Phosphate‐Modified In: Water Activation and Active Site Tuning

Electrochemical CO2 reduction reaction (CO2RR) offers a sustainable strategy for producing fuels and chemicals. However, it suffers from sluggish CO2 activation and slow water dissociation. In this work, we construct a (P‐O)δ− modified In catalyst that exhibits high activity and selectivity in electrochemical CO2 reduction to formate. A combination of in‐situ characterizations and kinetic analyses indicate that (P‐O)δ− has a strong interaction with K+(H2O)n, which effectively accelerates water dissociation to provide protons. In‐situ attenuated total reflectance surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) measurements together with density functional theory (DFT) calculations disclose that (P‐O)δ− modification leads to a higher valence state of In active site, thus promoting CO2 activation and HCOO* formation, while inhibiting competitive hydrogen evolution reaction (HER). As a result, the (P‐O)δ− modified oxide‐derived In catalyst exhibits excellent formate selectivity across a broad potential window with a formate Faradaic efficiency as high as 92.1% at a partial current density of ~200 mA cm−2 and a cathodic potential of ‐1.2 V vs. RHE in an alkaline electrolyte.