Visible Light Enhanced Electrocatalysis of Methanol Oxidation and Hydrogen Evolution on Nanoporous Nickel Hydroxide Film

In this work, high-surface-area nanoporous nickel hydroxide (Ni(OH)2) was one-pot electrodeposited by a dynamic hydrogen bubble template formed through facile water electrolysis. The as-obtained nanoporous Ni(OH)2 exhibited a visible light response semiconducting behavior with an optical band gap of 2.17 eV, as estimated by the Tauc methodology. The Mott-Schottky plot estimated the valence band (EVB) and conduction band (ECB) energies of the nanoporous Ni(OH)2 to −6.14 and −3.97 eV, respectively. The effects of visible light irradiation of nanoporous Ni(OH)2 film on methanol oxidation (MOR) and hydrogen evolution (HER) reactions were investigated in alkaline solutions. Compared to data obtained under dark, the potentiodynamic linear sweep voltammetry (LSV) and potentiostatic chronoamperometry (CA) results revealed remarkable enhancements in MOR and HER current responses using nanoporous Ni(OH)2 electrode under visible light, reaching up to 59% and 153%, respectively. The superior photoelectrochemical performances of the nanoporous Ni(OH)2 film toward MOR and HER were attributed to the high surface area, narrow band gap, low electron/hole recombination, and elevated light absorption efficiency induced by multiple reflection and scattering of incident light. In sum, the high photoelectrocatalytic performances of the nanoporous Ni(OH)2 combined with the low material cost and facile production make it promising for various electrochemical reactions with better reaction rates under visible light irradiation.