Hierarchical NiFeV hydroxide nanotubes: synthesis, topotactic transformation and electrocatalysis towards the oxygen evolution reaction.

Electrocatalytic overall water splitting is a sustainable approach to realizing the clean production of hydrogen energy; however, it is mainly hindered by the sluggish kinetics of the oxygen evolution reaction (OER). For large-scale hydrogen production, it is great urgent to develop efficient and low-cost OER electrocatalyst candidates from commercial noble metal-based materials. Herein, a facile template method was proposed for the preparation of a series of hierarchical NiFeV hydroxide nanotubes. With the combined advantages of a hierarchical nanostructure and the synergistic effect among multi-metal elements, the ternary hydroxides delivered outstanding OER performance. In particular, a low overpotential of 256.5 mV delivering a current density of 10 mA cm-2 with a Tafel slope of 52.4 mV dec-1 was achieved by hierarchical NiFeV hydroxide nanotubes with an initial Ni/Fe/V feed ratio of 8 : 1 : 1. After a subsequent topotactic transformation, ternary phosphide (denoted as NiFeVP) was obtained with the hierarchical nanostructure well maintained, and it achieved further performance enhancement where an overpotential of only 209.5 mV was required to deliver 10 mA cm-2 with a lower Tafel slope of 30.3 mV dec-1 and excellent durability for 50 h for chronopotentiometry even at 50 mA cm-2, demonstrating an admirable OER electrocatalyst.