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

The water-gas shift (WGS) reaction is often conducted at elevated temperature and requires energy-intensive separation of hydrogen (H 2 ) from methane (CH 4 ), carbon dioxide (CO 2 ), and residual carbon monoxide (CO). Designing processes to decouple CO oxidation and H 2 production provides an alternative strategy to obtain high-purity H 2 streams. We report an electrothermal WGS process combining thermal oxidation of CO on a silicomolybdic acid (SMA)-supported Pd single-atom catalyst (Pd 1 /CsSMA) and electrocatalytic H 2 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 CO 2 ${{_{{\rm CO}{_{2}}}}}$  mol Pd -1 achieving stable H 2 production with a purity consistently exceeding 99.99 %.