Novel vacancy-rich Co₃O₄/VO₂ nanohybrids for enhanced electrocatalytic performance and application as oxygen evolution electrocatalysts

Highlights: • A novel hollow and defect-rich Co₃O₄/VO₂ NHs are successfully prepared. • The interface effect of Co₃O₄/VO₂ NHs on its OER activity is studied. • Co₃O₄/VO₂ NHs possess abundant oxygen vacancy and heterostructured interfaces. • The excess electrons transfer from V to Co in C₃O₄/VO₂ NHs promotes the reactivity. • Co₃O₄/VO₂ NHs exhibit excellent electrocatalytic activity for OER. -- Abstract: Structure and defect control are effective strategies to manipulate the activity and stability of catalysts. Herein, a novel hollow and defect-rich Co₃O₄/VO₂ nanohybrids (NHs) is synthesized with zeolitic imidazolate framework-67 (ZIF-67) nanocrystal as the template to anchor VO₂ nanoparticles (NPs) for enhanced electrocatalytic performances. The changes of chemical composition, crystalline structure, oxygen vacancy concentration, phase boundaries of the interface between Co₃O₄ and VO₂ are detailedly studied by TEM, XPS, ESR and UV–vis absorbance spectra, so as to clarify the interface effect of nanohybrids comprising of two transition metal oxides on its OER activity. The as-prepared oxygen vacancy-rich Co₃O₄/VO₂ NHs show excellent electrocatalytic performance with a lower overpotential at the current density of 10 mA cm⁻² for oxygen evolution reaction (OER), which decreases in 100 mV as compared to that of Co₃O₄. These results confirm that the introduction of defect in the interface can not only provide more available catalytic active sites, but also efficiently stabilize the interfacial structure of the nanohybrids by depleting the stress. The greatly improved electrochemical performance of Co₃O₄/VO₂ NHs demonstrates the importance of rational design and control of vacancy defects, which may offer a step forward in the design of advanced hybrid nanomaterials.