Electrochemical template synthesis of hollow zinc oxide microtubes for photoelectrocatalytic water splitting: Effects of electrodeposition conditions and annealing temperature

In this paper, the problem of synthesizing hollow structures as a photoactive material for water electrolysis is addressed using the example of ZnO microtubes. In the study, a novel method of electrochemical template-assisted synthesis was applied to produce microtubes. The influence of zinc electrodeposition conditions (mode and electrolyte) and annealing on the photoelectrocatalytic (PEC) properties of the electrode material was evaluated. Samples prepared from citrate and zincate electrolytes were analyzed using scanning electron microscopy, energy dispersive X-ray mapping, X-ray diffraction, diffuse reflectance spectroscopy, photogalvanic response, voltammetry, and electrochemical impedance spectroscopy. The purpose of this paper was to demonstrate the advantages of using a citrate electrolyte over a classical zincate electrolyte for the electrochemical template method. It has been found that using citrate electrolyte allows for the production of ZnO microtubes that improve the PEC performance by 1.5–2 times. The effect of the synthesis conditions of the electrode material on the charge transfer resistance and diffusion limitations in the water splitting reaction is analyzed.