Joule heating to grain-boundary-rich RuP₂ for efficient electrocatalytic hydrogen evolution in a wide pH range

The production of storable hydrogen fuel through water splitting, powered by renewable energy sources such as solar photovoltaics, wind turbines, and hydropower systems, represents a promising path toward achieving sustainable energy solutions. Transition-metal phosphides (TMPs) have excellent physicochemical properties, making them the most promising electrocatalysts for hydrogen evolution reaction (HER). Traditionally, achieving good crystallinity in these TMPs typically requires prolonged (≥ 2 h) high-temperature pyrolysis, which is time-consuming and generally yields samples with large particle sizes, adversely affecting the catalytic activities. Herein, for the first time, we present a groundbreaking discovery in the synthesis of grain-boundary-rich RuP₂ nanoparticles within very short time frame of 9 seconds, using a fast Joule heating strategy (RuP₂ JH). Subsequent electrochemical tests reveal that the as-synthesized RuP₂ JH not only exhibits platinum-like HER activity, achieving overpotentials of 22, 22 and 270 mV to reach a current density of 10 mA cm^-2 in 0.5 M H₂SO₄, 1.0 M KOH, and 0.1 M phosphate buffered solutions, respectively, but also exhibits exceptional long-term stability. Moreover, it exhibits a Faradaic efficiency exceeding 96%. This work significantly contributes to the expanding repertoire of TMPs synthesized via Joule heating by showcasing exceptional performance toward HER and other energy-related catalytic applications.