Facile self-oxidized Ni nano-foam as high-performance catalyst for hydrogen and oxygen evolution

Abstract

Development of high-performance catalysts with facile, self-supporting, simple and noble-metal-free features for hydrogen and oxygen evolution reactions (HER and OER) is a long-lasting pursuit. Herein, a facile self-oxidized Ni nano-foam with self-supporting nanoporosity is obtained by single-step dealloying of Mg80Ni20 metallic glass ribbons. The Ni nano-foam exhibits superior HER performance with an overpotential of 33.1 and 71.4 mV at the current density of 10 and 100 mA cm−2, and low OER overpotential of 330 mV at 10 mA cm−2. Outstanding long-term stability up to 100 h is confirmed for both HER and OER. A water electrolyzer based on the Ni nano-foam couple shows good stability and remarkable activity for overall water splitting, which requires 1.58 V to reach 10 mA cm−2. The geometry features of the Ni nano-foam, i.e., three-dimensional structure, ultrafine size, high porosity and large surface area are highly beneficial for catalytic activity. The synergic effect of the Ni/NiO composite at the ligament skin is confirmed to decrease the free energy for hydrogen binding, facilitate the H−OH bond breaking and accelerate OH− ion formation, which significantly improves the intrinsic HER activity. The outstanding HER and OER performances of the self-oxidized Ni nano-foam validate the metal nano-foams as promising catalyst candidates, especially in view of the ultrafine nanoporous, self-supporting, composition regulation, single-step synthesis and massive fabrication features. [Figure not available: see fulltext.]