Pearson's principle-inspired strategy for the synthesis of amorphous transition metal hydroxide hollow nanocubes for electrocatalytic oxygen evolution

Abstract

Hollow nanostructures with higher surface area offer great advantages for electrocatalytic water splitting. Here, we demonstrate the fabrication of amorphous hollow M(OH)_x (M = Fe, Co, Ni) nanocubes through a template-assisted route inspired by Pearson's hard and soft acid–base (HSAB) principle with Cu₂O nanocubes with different sizes (50 nm, 500 nm) as the sacrificial templates. A comparative study of the electrocatalytic oxygen evolution reaction (OER) of the hollow M(OH)_x nanocubes with a similar size indicates that Ni(OH)₂ has better OER catalytic activity. It has been revealed that the metal oxyhydroxides formed at the surface are actually the real active species for the OER electrocatalysis. In particular, Ni(OH)₂ nanocubes obtained by the Cu₂O (50 nm) template provide the best OER activity, with a low overpotential of 349 mV vs. RHE to achieve a current density of 10 mA cm⁻² and a low Tafel slope of 63 mV dec⁻¹. The hollow metal hydroxide nanostructures through the Pearson's principle-inspired strategy can be highly efficient electrocatalysts for OER applications.