Highly dispersed ultra-small RuO2 nanoparticles on NiO nanosheet arrays as efficient pH-universal hydrogen evolution electrocatalysts

Developing efficient Pt-free electrocatalysts for hydrogen evolution reaction (HER) at all pHs remains challenging for large-scale hydrogen production, especially in alkaline and neutral conditions, because of sluggish water dissociation. Herein, the synthesis of novel highly dispersed RuO2 nanoparticles on NiO nanosheet arrays (RuO2/NiO/NF) with efficient pH-universal HER electrocatalysis via a simple in situ growth and sequential calcination process is reported. The as-prepared RuO2/NiO/NF nanosheet arrays exhibit outstanding HER performance with overpotentials of 31, 66, and 84 mV to deliver 10, 100, and 300 mA cm−2, respectively, in 1.0 M KOH, outperforming even the commercial Pt/C electrocatalyst. In addition, RuO2/NiO/NF shows a higher turnover frequency at an overpotential of 100 mV in comparison with Pt/C electrocatalyst. It also requires extremely low overpotentials of 98 mV and 254 mV to afford 300 mA cm−2 in 0.5 M H2SO4 and 1.0 M PBS-neutral solution, respectively. Moreover, RuO2/NiO/NF can work at 100 mA cm−2 for 200 h with negligible decay in 1.0 M KOH. The splendid HER performance can be ascribed to the 3D nanosheet arrays and highly dispersed RuO2 nanoparticles with richly exposed active sites, favoring the efficient electron and mass transfer to the active sites.