Multi-hierarchical Ni(OH)2/NiOOH 2D-nano-flaked electrocatalyst substrate for efficient oxygen evolution reaction

Abstract

Electrocatalytic oxygen evolution reaction (OER) catalyzed by earth-abundant non-precious metals and their compounds is an attractive area of research for electrocatalytic hydrogen generation from water splitting. However, producing non-noble metal-based OER electrocatalysts that are stable and efficient in alkaline medium is challenging. In this work, we used a combination of femtosecond laser surface structuring and hydrothermal treatment to create multi-hierarchical Ni(OH)2/NiOOH nanostructures directly on Ni foam. Owing to a large electrochemically active surface area, the multi-hierarchical electrode demonstrates an excellent OER performance in an alkaline medium with low (η1 = 162 mV) onset and overpotential (η10 = 319 mV) values and a small Tafel slope of 49 mV dec−1. The femtosecond laser structuring creates laser-induced periodic surface structures (LIPSSs) where surfaces of ∼130 nm wide grooves and ∼270 nm wide ridges are covered with sub-nanoscale particles. The hydrothermal treatment produces vertically aligned two-dimensional Ni(OH)2/NiOOH nanoflakes on the grooves and ridges of the LIPSSs. This work provides a simple, scalable, and sustainable approach to producing high-efficiency electrocatalysts and battery electrodes from regular metal sheets and foams.