Boosting alkaline water splitting efficiency: NiOOH–MnOOH heterojunctions via in situ anodic oxidation†

Abstract

Designing noble metal-free electrocatalysts remains a challenge for the oxygen evolution reaction (OER) in alkaline solutions. In this study, we present a facile electrodeposition approach coupled with an in situ anodic oxidation method to synthesize NiOOH–MnS/NF on nickel foam (NF), successfully creating NiOOH–MnOOH/NF heterojunctions to boost OER performance under alkaline conditions. The heterojunction's synergistic effect significantly modulates the adsorption energy of the rate-determining step (RDS), thereby enhancing the intrinsic electrocatalytic activity of the NiOOH–MnOOH/NF electrocatalyst. Furthermore, the introduction of SO₄²⁻ leads to a variable degree of electron loss in both Mn and Ni, reducing adsorption strength of the OER intermediates and thus optimizing reaction kinetics. The as-prepared NiOOH–MnOOH/NF electrocatalyst demonstrates exceptional OER performance in 1.0 M KOH, achieving a current density of 100 mA cm⁻² with a Tafel slope of 52.3 mV dec⁻¹ and a minimal overpotential of 391 mV. Utilizing NiOOH–MnOOH/NF as a bifunctional electrode for overall water splitting (OWS), the system operates at a low potential of 1.66 V at 10 mA cm⁻², showcasing its excellent durability. This work offers novel insights and promising prospects for the advancement and practical application of non-precious metal electrocatalysts in the field of electrocatalytic water splitting.