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In this paper, we have engineered the interface electronic structure in Cu2O/ZnO nanorod arrays, via adjusting the carrier concentration of Cu2O, and applied them to photocatalysis. The photoinduced charge transfer kinetics at the interface between Cu2O and ZnO were systematically investigated. The Cu2O (pH 11.0)/ZnO nanorod arrays have the largest magnitude of interfacial electric field, and photoinduced charge carriers can be separated rapidly and efficiently, which generates the highest photocatalytic efficiency for the reduction of methylviologen. Heterojunction construction is an exciting direction to pursue for highly active photocatalysts, and also offers opportunities to investigate the relationship between the electronic structure and the photocatalytic performance.

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In this work, tungsten oxide (WO3) with three-dimensional flower-like and wheel-like architectures, based on the spontaneous aggregation of one-dimensional nanorods, were successfully fabricated by adjusting the pH of the precursor solution. The influence of pH on the morphologies of WO3 was systematically studied, and the different WO3 architectures were used to photocatalytically degrade rhodamine B. The kinetic features of photoinduced charges of as-prepared WO3 have been investigated by surface photovoltage spectroscopy and transient photovoltage techniques in detail. WO3 with wheel-like and flower-like structures possess the higher charge separation efficiency and the lower recombination rate of photoinduced charges, resulting in higher photocatalytic activity for the degradation of RhB.

For semiconductor-based PEC systems, loading an appropriate cocatalyst on a semiconductor (such as a solar-active material) can significantly improve the PEC activity due to the suppression of photogenerated charge recombination. But there is little direct information about the role of a cocatalyst in the spatial separation of photogenerated charge carriers. In our work, a combination of surface photovoltage spectroscopy (SPS), transient photovoltage (TPV) technique, photoelectrochemical impedance spectroscopy (PEIS) and transient photocurrent measurements was used to study the real role of Ni(OH)2 as a cocatalyst for the enhanced PEC performance of Ni(OH)2-modified Ti-doped α-Fe2O3. It was found that Ni(OH)2 as a hole storage layer enhances the separation of photogenerated charge carriers and increases the lifetime of holes, which contributed to the enhanced photocurrent. In addition, Ni(OH)2 is a good cocatalyst for urea oxidation which suppresses the over-potential, resulting in a negative shift of the onset potential.