A General Method for Controllably Constructing Nanoarray Catalysts of Transition-Metal Nanoparticles Loaded on Zinc Oxide Nanowires

An array catalyst is promising to lead the way for future developments of high-performance catalysts, owing to its large specific surface area, excellent activity, stability, and reusability. Herein, a series of new candidates, i.e., the transition-metal nanoparticles supported on zinc oxide nanowires (TM/ZnO), are introduced into this catalytic system. The free-standing TM/ZnO nanoarray catalysts can be controllably constructed on the conductive substrate through a flexible, economical, and scalable approach combining electrodeposition and hydrothermal reaction and exhibit very high photocatalytic activity toward the reduction reaction of nitrate to ammonia. The results demonstrate that the catalytic activity of TM/ZnO primarily originates from iron (Fe), cobalt (Co), nickel (Ni), or copper (Cu) nanoparticles, rather than the ZnO nanoarray and stainless steel substrate. When the structure and composition are very close, the photocatalytic activity of Co/ZnO for the nitrate reduction reaction is significantly superior to those of Cu/ZnO, Ni/ZnO, and Fe/ZnO, possibly owing to its smaller charge-transfer resistance and bigger photocurrent. This universal synthetic methodology paves a novel avenue for developing other ZnO nanoarray-supported metal catalysts, showing great prospects in environmental and energy-related applications.