Highly dispersed ultra-small RuO 2 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 RuO 2 nanoparticles on NiO nanosheet arrays (RuO 2 /NiO/NF) with efficient pH-universal HER electrocatalysis via a simple in situ growth and sequential calcination process is reported. The as-prepared RuO 2 /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, RuO 2 /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 H 2 SO 4 and 1.0 M PBS-neutral solution, respectively. Moreover, RuO 2 /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 RuO 2 nanoparticles with richly exposed active sites, favoring the efficient electron and mass transfer to the active sites.