Sulfate-Functionalized Nickel Hydroxide Nanobelts for Sustained Oxygen Evolution

Nickel hydroxide (Ni(OH)2)-based electrocatalysts are promising for the oxygen evolution reaction (OER) due to their low cost, but their activity and durability still need substantial improvement to meet practical application. Here, we report a sulfate-functionalized Ni(OH)2 nanobelt (S-Ni(OH)2) electrocatalyst, which exhibited self-enhanced OER activity due to its self-renewed surface during anodic oxidation. The S-Ni(OH)2 was in situ grown on the nickel foam (NF) surface in potassium peroxydisulfate solution through one-step hydrothermal treatment. This material outperformed all the existing electrocatalysts in the intensity and duration of the OER activity enhancement. An overpotential drop of 70 mV is shown by the S-Ni(OH)2/NF electrode during 110 h reaction at a current density of 100 mA cm-2, and the overpotential remains as low as 358 mV at a current density of 200 mA cm-2. Such activity enhancement during OER is mainly ascribed to the formation of a highly active NiOOH/Ni(SO4)0.3(OH)1.4 composite on the S-Ni(OH)2 surface as a result of gradual sulfate release. Given the facile and environmentally benign fabrication process (without external addition of a Ni source and surfactant) and good electrochemical properties (high activity and long lifetime), the S-Ni(OH)2 holds great potential for practical OER application. The surface self-renewal strategy developed here might also be expanded to other electrocatalysts and electrochemical processes.