Mesoporous In2O3 nanoflowers with oxygen vacancies for both alkaline and acidic CO2 electroreduction to formate/formic acid

Abstract

The CO₂ reduction reaction (CO₂RR) is desirable, yet catalysts that exhibit high activity across different pH levels are lacking. Herein, mesoporous In₂O₃ nanoflowers (In₂O₃ NFs) with abundant oxygen vacancies (O_V) are prepared by calcining an In₂S₃ precursor, which can selectively reduce CO₂ to formate/formic acid. The In₂O₃ NFs deliver 88.4% formate faradaic efficiency (FE) at 500 mA cm⁻² in a flow cell under alkaline conditions (pH = 13.5). Impressively, a high formic acid FE of ∼90% from 100 to 600 mA cm⁻² is achieved in an acidic solution (pH = 2), representing one of the most promising acidic CO₂RR performances to date. The confinement effect of the porous structure could enrich K⁺ ions to enhance the local alkaline microenvironment at the electrode interface during acidic CO₂RR, which is the key to inhibiting the hydrogen evolution reaction (HER) and protecting the catalyst against acid corrosion. This work provides an efficient electrocatalyst for CO₂RR in both alkaline and acidic electrolytes.