Three-dimensional porous metal phosphide cathode electrodes prepared via electroless galvanic modification for alkaline water electrolysis

Green hydrogen production from water electrolysis is crucial to propelling power-to-X strategies, and a central role in this strategy depends on innovative catalysts used in different electrolyzer technologies. The present study combines galvanic replacement and low-temperature annealing to construct a self-supported and low Ru-loaded metal phosphide electrode for efficient alkaline hydrogen evolution reaction (HER). The non-platinum electrode (catalyst + porous transport layers) fabricated over three-dimensional nickel foam (Ni2P-Ru/NF) yielded an overpotential of 40 mV for 10 mA cm(-2) in 1 M KOH during the HER and also demonstrated excellent durability under varying conditions for 48 h. A comprehensive analysis of surface characteristics followed by first principles calculations specified the factors, surface modification and active sites favoring excellent HER performance for Ni2P-Ru/NF. The most favorable hydrogen adsorption (Delta G(H*)) value, from DFT calculations, was identified for the Ru site in Ni2P-Ru, which was also very similar to the Pt/C system. Finally, the overall water splitting study performed using the Ni2P-Ru/NF catalyst as the cathode (Ni2P-Ru/NF||IrO2) showed the compatibility of the self-supported catalyst for efficient electrolysis with a noteworthy performance of 1.6 V for 10 mA cm(-2). The study showcases a potential pathway for applying very low Ru-loaded, self-supporting and carbon-free metal phosphide electrodes in commercial water electrolyzer systems for efficient green hydrogen generation.

Automated summary

This study presents a self-supported and low Ru-loaded metal phosphide electrode for efficient alkaline hydrogen evolution reaction (HER) through galvanic replacement and low-temperature annealing. The electrode exhibited excellent HER performance and durability, and the factors affecting the performance were analyzed through surface characteristics and first principles calculations. Water splitting studies demonstrated the compatibility and noteworthy performance of the catalyst for efficient electrolysis, showcasing its potential in commercial water electrolyzer systems for green hydrogen generation.