Surface strain engineered Ni-NiO for boosting hydrogen evolution reaction in alkaline media

Abstract

Electrolysis of water in alkaline media to produce hydrogen is a green and promising energy storage technology, but the kinetically sluggish hydrogen evolution reaction (HER) in alkaline electrolytes limits its development, requiring cheap and highly efficient catalysts to increase the HER rate. The HER activity of transition metal-based catalysts is closely associated with the d-band structures. Herein, the surface strain of Ni and NiO was engineered to regulate the d-band centers and the HER activity. DFT calculations found that the Ni(111) supported NiO(111) shows expanded surface lattice compared to the unsupported NiO(111), and the NiO(100) supported Ni(100) shows compressed surface lattice compared to the unsupported Ni(100), leading to ∼2 eV upshift and downshift of d-band centers of the surface Ni atoms, respectively. Guided by the DFT calculation, the surface-oxidized Ni (so-Ni) and surface-reduced NiO (sr-NiO) catalysts were synthesized and shows expanded and compressed surface lattice respectively, leading to enhanced HER activity. The synthesized sr-NiO shows the highest HER activity with an overpotential of 164 mV to deliver a current density of 10 mA cm−2, which outperforms many of the recently reported Ni-based HER catalysts in alkaline electrolytes.