Loading FeOOH on Ni(OH) hollow nanorods to obtain a three-dimensional sandwich catalyst with strong electron interactions for an efficient oxygen evolution reaction.

Sustainable production of hydrogen by water splitting requires the exploration of highly efficient electrocatalysts from abundant non-precious metals on Earth. Ni(OH)2 hollow nanorod arrays were obtained on Ni foam by simple alkali etching, and FeOOH was electrodeposited on the walls of hollow nanorods to construct FeOOH@Ni(OH)2 sandwich hollow nanorod arrays, which help overcome the drawbacks of the poor conductivity and poor stability of FeOOH and boost the catalytic performance of the oxygen evolution reaction (OER) in comparison with the individual components. A fully contacted three-dimensional nanorod array structure provides many exposed catalytically active sites and promotes charge transfer during the electrochemical OER process. The presence of FeOOH can promote the formation of a more conductive catalytically active component, NiOOH, which improves the catalytic performance of Ni(OH)2. The electronic interaction and synergistic catalysis between nickel and iron enhances the electrochemical performance of the catalyst significantly. The optimized FeOOH@Ni(OH)2 sandwich hollow nanorod arrays show an outstanding OER activity with a small overpotential of 245 mV at 50 mA cm-2 and a low Tafel slope of 45 mV dec-1. The catalyst can maintain a substantially constant voltage over 40 h in 1.0 M KOH solution. Our work provides a new strategy to prepare Ni-Fe bimetallic materials as OER electrocatalysts.