Self-Supported\nPorous Carbon Monoliths for Electrocatalytic\nHydrogen Evolution in Alkaline Freshwater and Seawater

Developing efficient catalysts for seawater electrolysis\nhydrogen\nevolution reaction (HER) is crucial for producing green hydrogen.\nCarbonized wood (CW), a porous carbon monolith, is a promising self-supporting\nelectrocatalytic electrode owing to its environmentally friendly,\nsustainable, and hierarchically porous properties. However, the impact\nof different tree species on the hydrogen evolution performance remains\nunclear. In this study, various types of CWs, including carbonized\npoplar (PoCW), carbonized balsa (BaCW), carbonized fir (FiCW), and\ncarbonized pine (PiCW), have been selected to investigate their electrocatalytic\nperformance in hydrogen evolution. Among these, the PoCW exhibits\nsuperior electrocatalytic HER performance compared to the other CWs,\nattributed to its electrochemically active surface area, resistance,\nand the content of oxygen-containing functional groups. PoCW demonstrates\na low overpotential of 284 mV and 356 mV at 10 mA cm<sup>–2</sup> in alkaline freshwater and seawater, respectively. Moreover, PoCW\nshows long-term durability for 100 h in both alkaline freshwater and\nseawater. This work guides the selection of wood-based carbon monoliths\nand demonstrates that metal-free, CW-based self-supporting electrodes\nhold great potential for electrocatalytic hydrogen evolution in both\nfreshwater and seawater.