Synergistic design of embedded heterojunctions and hollow architecture for superior HER in acidic and alkaline electrolytes

Ruthenium phosphide electrocatalysts for the hydrogen evolution reaction (HER) still face challenges such as insufficient active site utilization and limited durability. This work addresses these challenges via a synergistic strategy that integrates heterojunction engineering with a hollow confinement structure, resulting in RuP₂-Ni₂P nanoparticles embedded within N,P-codoped hollow carbon spheres (RuP₂-Ni₂P/NPC). The interfacial coupling between RuP₂ and Ni₂P optimizes the electronic structure toward a near-ideal hydrogen adsorption energy, while the unique embedded architecture ensures abundant accessible active sites and exceptional structural robustness. As a result, the RuP₂-Ni₂P/NPC catalyst exhibits superior HER performance across a wide pH range, achieving ultralow overpotentials of 3 mV in 1 M KOH and 17.3 mV in 0.5 M H₂SO₄ at 10 mA·cm⁻², ranking among the best of reported RuP₂-based catalysts. It also demonstrates excellent long-term durability in both alkaline and acidic electrolytes. This work provides a feasible design strategy toward efficient and robust electrocatalysts for hydrogen production.