Nickel-ruthenium nanoalloy encapsulated in mesoporous carbon as active electrocatalysts for highly efficient overall water splitting in alkaline solution

Abstract A nickel-ruthenium nanoalloy embedded within a mesoporous carbon matrix (NiO@RuO2@mC) is developed by calcinating NiNi Prussian blue analogue doped with trace Ru3+ in air atmosphere as an efficient electrocatalyst for overall water splitting in alkaline medium. The produced NiO@RuO2@mC nanoparticles (NPs) display a loose porous structure, which can remarkably facilitate mass transfer and bubble diffusion during electrocatalysis. RuO2 NPs can tune the electronic structure of Ni and decrease charge-transfer resistance, further leading to fast electron transport and enhancing the intrinsic electrocatalytic activities. The developed NiO@RuO2@mC catalyst demonstrates good stability, long-term durability, and excellent electrocatalytic oxygen evolution reaction and promising hydrogen evolution reaction in alkaline medium. For oxygen evolution reaction, the catalyst shows a low overpotential of 170 mV for obtaining a current density of 10 mA cm−2 and a small Tafel slope of 57 mV dec−1; for hydrogen evolution reaction, it shows an overpotential of −129 mV for delivering a current density of 10 mA cm−2 and a Tafel slope of 120 mV dec−1. Consequently, when NiO@RuO2@mC catalyst is used as a two-electrode alkaline electrolyzer for water splitting, a current density of 30 mA cm−2 is achieved at a low cell voltage of 1.52 V.