Densely populated tiny RuO₂ crystallites supported by hierarchically porous carbon for full acidic water splitting

The exploitation of highly active bifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acidic media has been a subject receiving immense interest. However, the existing catalysts usually suffer from low catalytic efficiency and poor corrosion resistance under acidic conditions. Herein, we report a facile molten salt method to fabricate ruthenium dioxide nanoparticles supported by hierarchically porous carbon (RuO₂/PC) as a bifunctional electrocatalyst for full water splitting under strong acidic conditions. The formation of a densely populated nanocrystalline RuO₂/carbon heterostructure helps expose catalytic sites, accelerates the mass transfer rate, and further enhances the acid resistance of RuO₂ nanoparticles. The as-synthesized RuO₂/PC consequently exhibits superior catalytic performance for the OER with an overpotential of 181 mV upon 10 mA cm^-2 compared to that of the commercial RuO₂ (343 mV) and a comparable performance to Pt/C for the HER (47.5 mV upon 10 mA cm^-2) in 0.5 M H₂SO₄. The RuO₂/PC shows promising stability with little degradation over ∼24 h. Impressively, the water electrolyzer based on RuO₂/PC shows an overpotential of 326 mV at 10 mA cm^-2, much lower than that of the electrolyzer based on the combination of Pt/C and RuO₂ (400 mV), indicating its great potential towards practical application.