In Situ Engineering Multifunctional Active Sites of Ruthenium–Nickel Alloys for pH‐Universal Ampere‐Level Current‐Density Hydrogen Evolution

Abstract Developing robust non‐platinum electrocatalysts with multifunctional active sites for pH‐universal hydrogen evolution reaction (HER) is crucial for scalable hydrogen production through electrochemical water splitting. Here ultra‐small ruthenium‐nickel alloy nanoparticles steadily anchored on reduced graphene oxide papers (Ru‐Ni/rGOPs) as versatile electrocatalytic materials for acidic and alkaline HER are reported. These Ru–Ni alloy nanoparticles serve as pH self‐adaptive electroactive species by making use of in situ surface reconstruction, where surface Ni atoms are hydroxylated to produce bifunctional active sites of Ru‐Ni(OH)₂ for alkaline HER, and selectively etched to form monometallic Ru active sites for acidic HER, respectively. Owing to the presence of Ru‐Ni(OH)₂ multi‐site surface, which not only accelerates water dissociation to generate reactive hydrogen intermediates but also facilitates their recombination into hydrogen molecules, the self‐supported Ru₉₀Ni₁₀/rGOP hybrid electrode only takes overpotential of as low as ≈106 mV to deliver current density of 1000 mA cm⁻², and maintains exceptional stability for over 1000 h in 1 m KOH. While in 0.5 m H₂SO₄, the Ru₉₀Ni₁₀/rGOP hybrid electrode exhibits acidic HER catalytic behavior comparable to commercially available Pt/C catalyst due to the formation of monometallic Ru shell. These electrochemical behaviors outperform some of the best Ru‐based catalysts and make it attractive alternative to Pt‐based catalysts toward highly efficient HER.