Electrothermal Water-Gas Shift Reaction at Room Temperature with a Silicomolybdate-Based Palladium Single-Atom Catalyst

Abstract

The water-gas shift (WGS) reaction is often conducted at elevated temperature and requires energy-intensive separation of hydrogen (H₂ ) from methane (CH₄ ), carbon dioxide (CO₂ ), and residual carbon monoxide (CO). Designing processes to decouple CO oxidation and H₂ production provides an alternative strategy to obtain high-purity H₂ streams. We report an electrothermal WGS process combining thermal oxidation of CO on a silicomolybdic acid (SMA)-supported Pd single-atom catalyst (Pd₁ /CsSMA) and electrocatalytic H₂ evolution. The two half-reactions are coupled through phosphomolybdic acid (PMA) as a redox mediator at a moderate anodic potential of 0.6 V (versus Ag/AgCl). Under optimized conditions, our catalyst exhibited a TOF of 1.2 s^-1 with turnover numbers above 40 000 mol ${}_{\mathrm{CO}{}_2}$ mol_Pd ^-1 achieving stable H₂ production with a purity consistently exceeding 99.99 %.

Keywords: High-Purity Hydrogen; Hydrogen Evolution Reaction; Indirect Electrocatalysis; Polyoxometalate.