In Situ Grown Epitaxial Heterojunction Exhibits High-Performance Electrocatalytic Water Splitting

Electrocatalytic performance can be enhanced by engineering a purposely designed nanoheterojunction and fine-tuning the interface electronic structure. Herein a new approach of developing atomic epitaxial in-growth in Co-Ni₃N nanowires array is devised, where a nanoconfinement effect is reinforced at the interface. The Co-Ni₃N heterostructure array is formed by thermal annealing NiCo₂O₄ precursor nanowires under an optimized condition, during which the nanowire morphology is retained. The epitaxial in-growth structure of Co-Ni₃N at nanometer scale facilitates the electron transfer between the two different domains at the epitaxial interface, leading to a significant enhancement in catalytic activities for both hydrogen and oxygen evolution reactions (10 and 16 times higher in the respective turn-over frequency compared to Ni₃N-alone nanorods). The interface transfer effect is verified by electronic binding energy shift and density functional theory (DFT) calculations. This nanoconfinement effect occurring during in situ atomic epitaxial in-growth of the two compatible materials shows an effective pathway toward high-performance electrocatalysis and energy storages. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim