Hierarchically porous carbon wood sponge decorated with bimetallic sites: A highly efficient electrocatalyst for hydrogen evolution in universal-pH electrolytes and seawater

Designing low-cost, non-noble metal electrocatalysts for complex seawater-splitting processes remains a significant challenge. In this study, we report a highly efficient electrocatalyst composed of Fe-Co alloy-embedded MXene nanosheets grown on a nitrogen and carbon-doped, low-tortuosity, hierarchically porous wood carbon sponge (FeCo@CN/MXene/CS). This FeCo@CN/MXene/CS catalyst, with its porous layered structure, demonstrates exceptional bifunctional electrocatalytic performance, including remarkable electrochemical activity and stability in seawater. Notably, in 0.5 M H₂SO₄ and 1.0 M KOH, the catalyst exhibits overpotentials of 70 mV and 64 mV, respectively, for the hydrogen evolution reaction (HER) at a current density of 10 mA cm⁻². Furthermore, it shows excellent catalytic activity and durability in natural seawater, with only a slight decrease in HER activity after 5000 cyclic voltammetry (CV) cycles and negligible degradation after 20 h of continuous electrolysis. The outstanding performance of FeCo@CN/MXene/CS is attributed to its ability to lower the energy barrier for water dissociation, optimize the adsorption and desorption of H* intermediates, and facilitate rapid mass transfer through its porous structure, as supported by both density functional theory and experimental results. This research presents a novel approach for converting abundant biomass resources into highly efficient electrocatalysts, enhancing electrocatalytic hydrogen production in natural seawater.