Three-Dimensional Nickel Cobalt Phosphide Nanocrosses with Well-Defined Axial Arms for Efficient Oxygen Evolution Reaction.

Concave nanostructure with highly branched architecture and abundant step atoms is one kind of desirable materials for energy conversion devices. However, current synthetic strategies for non-noble metal-based NiCoP concave nanostructure still remain challenging. Herein, we demonstrate a site-selective chemical etching and subsequent phosphorating strategy to fabricate highly branched NiCoP concave nanocrosses (HB-NiCoP CNCs). The HB-NiCoP CNCs are consisted of six axial arms in three-dimensional space and each protruding arm is equipped with high-density atomic steps, ledges and kinks. As an electrocatalyst towards oxygen evolution reaction, the HB-NiCoP CNCs exhibit remarkably enhanced activity and stability, with small overpotential of 289 mV to reach 10 mA cm-2 , surpassing the NiCoP nanocages and commercial RuO2 . The superior OER performance of HB-NiCoP CNCs is originated from the highly branched concave structure, the synergistic effect between bimetal Ni and Co atoms, as well as the electronic structure modulation from P.