Heterostructured metal oxides realized by quenching-induced structural transformation

Heterostructured metal oxides exhibit outstanding catalytic performance in various chemical/electrochemical reactions, yet still face the bottleneck of synthesis difficulty and insufficient control over the catalyst composition. Herein, a facile synthesis route for heterostructured metal oxides via quenching-induced structural transformation was developed, and the size effect and the promotion mechanism between multiple quenching are also presented. Repeated quenching of hot NiMoO4 powders with a broad range of initial particle size in cold Fe(NO3)(3) solution yielded different products depending on the initial NiMoO4 particle size and quenching frequency. Significant disorder and a roughened surface were created on the large-grained NiMoO4 nanoparticles (>27 nm), whilst for smaller NiMoO4 nanoparticles (<27 nm), multiple quenching triggered the structural transformation from NiMoO4 to NiFe2O4 to create a novel NiMoO4/NiFe2O4 heterostructure. We further found that the disordered defect structure generated by pre-quenching can promote the subsequent quenching regulation, and the minimization of particle size was more sensitive to quenching and thus was regulated as a whole, overcoming the thermodynamic bottleneck. The NiMoO4/NiFe2O4 heterostructured nanocatalyst demonstrated remarkable catalytic activity for oxygen evolution and reduction reactions in alkaline media, thus delivering excellent electrochemical performance in rechargeable zinc-air batteries. Our findings provide novel inspiration for the preparation of highly active heterostructured metal oxide nanocatalysts, which can be applied to various oxides, such as CoMoO4/CoFe2O4.