Acid promoted Ni/NiO monolithic electrode for overall water splitting in alkaline medium

Exploring and designing bi-functional catalysts with earth-abundant elements that can work well for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline medium are of significance for producing clean fuel to relieve energy and environment crisis. Here, a novel Ni/NiO monolithic electrode was developed by a facile and cost-effective acid promoted activation of Ni foam. After the treatment, this obtained monolithic electrode with a layer of NiO on its surface demonstrates rough and sheet-like morphology, which not only possesses larger accessible surface area but also provides more reactive active sites. Compared with powder catalysts, this monolithic electrode can achieve intimate contact between the electrocatalyst and the current collector, which will alleviate the problem of pulverization and enable the stable function of the electrode. It can be served as an efficient bi-functional electrocatalyst with an overpotential of 160 mV for HER and 290 mV for OER to produce current densities of 10 mA cm(-2) in the alkaline medium. And it maintains benign stability after 5,000 cycles, which rivals many recent reported noble-metal free catalysts in 1.0 mol L-1 KOH solution. Attributed to the easy, scalable methodology and high catalytic efficiency, this work not only offers a promising monolithic catalyst but also inspires us to exploit other inexpensive, highly efficient and self-standing noble metalfree electrocatalysts for scale-up electrochemical water-splitting technology.