Surface self-reconstruction of nickel foam triggered by hydrothermal corrosion for boosted water oxidation

Abstract Electrochemical water splitting, as a promising approach to convert renewable electricity sources into chemical energy, is limited by bottleneck reaction of oxygen evolution (OER), and requires efficient/low-cost catalysts to accelerate OER dynamics. Metallic Ni, generally as the cathode of industrial alkali electrolyzer toward H2 production, is affordable yet inactive for anodic OER process. Enabling Ni metal with high OER activity directly serving as the anode will be an exciting progress, and undoubtedly full of challenges. Here, unexpectedly, metallic Ni demonstrates OER vitality through a superficial morphological reconstruction of Ni foam (NF) via hydrothermal-etching. The surface morphological change achieves Ni hierarchical nanosheet@nanoparticle array structure (r-Ni-1), ensuring the realization of optimal electrolyte contact and more surface exposure. More importantly, such configuration benefits for further achievement of fast transformation (in several seconds) into metal oxides and/or (oxy)hydroxides during the catalysis which are believed as the real active species. Above-mentioned in-situ transformation for conventional NF generally requires high-temperature treatment or long-term electrochemical activation for several hours. The catalytic performance of r-Ni-1 indeed outperforms most bimetallic catalysts with overpotential of 330 mV to yield 60 mA cm−2 in 1.0 M KOH, and it shows no obvious decay after a 60 h test. Our findings not only present a high-performance OER electrocatalyst, but also offer a possibility toward the simple preparation of anode materials for scale-up alkali electrolyzers.