Ag-modified Pd-based catalysts for hybrid electrolyzer: Breaking the C–C bond in glycerol to drive energy-efficient hydrogen production

Coupling hydrogen evolution reaction (HER) with glycerol oxidation reaction (GOR) in a hybrid electrolyzer represents a highly promising approach for green hydrogen production and glycerol upgrading. However, the limited activity and stability of existing GOR catalysts restrict the energy efficiency of the coupled system. In this study, Pd/C and Pd 4 Ag x /C catalysts were synthesized to investigate the impact of Ag on the activity and stability of Pd-based catalysts for GOR. The optimized Pd 4 Ag 8 /C demonstrated a specific activity of 17.4 ± 0.1 mA cm −2 Pd and a mass activity of 13.2 ± 0.3 A mg −1 Pd , both being more than 10 times higher than those of Pd/C. Combined results of ultra-performance liquid chromatography and density functional theory calculations revealed that the introduction of Ag promotes C−C cleavage in glyceric acid on Pd sites, facilitating electron transfer in GOR and thereby enhancing the GOR activity. The GOR coupled HER hybrid electrolyzer using Pd 4 Ag 8 /C as the GOR catalyst achieved a significant reduction of ∼1.07 V in cell voltage compared to conventional water electrolysis system at a current density of 10 mA cm −2 with a favorable operational stability, and realized the production of high-value-added chemicals, demonstrating the promising potential in both hydrogen production and upgrade of glycerol.