Selective CO-to-hydrocarbon conversion in formic acid–promoted borohydride hydrolysis for PEMFC-grade hydrogen production

Formic acid (FA)–mediated sodium borohydride (SBH) hydrolysis offers high system-level hydrogen storage density for on-board PEMFC applications, but often generates transient CO concentrations due to FA decomposition far exceeding the CO tolerance of PEMFC anodes. Existing CO removal strategies are limited in delivering sub-ppm level CO impurity, fast dynamic response, and thermal compatibility. Here, CO impurity is selectively converted to condensable, adsorption-separable C 3+ hydrocarbons via a Fischer–Tropsch–like reaction over Ru/TiO 2 /Al 2 O 3 , reducing CO from ∼10,000 ppm to <1 ppm at 120–160 °C and 20–40 barg. The integrated SBH H 2 generator–purifier–PEMFC system operated continuously for 48 h without performance degradation under realistic transients. The catalyst maintained stable performance over 100 h in scaled-up configuration. Heat-balance analysis shows that SBH hydrolysis exothermicity is sufficient to sustain purifier operation without continuous external heating during steady-state operation, demonstrating feasibility of a compact, thermally self-sustained on-board hydrogen supply system.