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Modification is one of the most important and effective methods to improve the photoelectrocatalytic (PEC) performance of ZnO. In this paper, the RuxZn1−xO/Ti electrodes were prepared by thermal decomposition method and the effect of Ru content on those electrodes’ electronic structure was analyzed through the first-principles calculation. Various tests were also performed to observe the microstructures and PEC performance. The results showed that as the Ru4+ transferred into ZnO lattice and replaced a number of Zn2+, the conduction band of ZnO moved downward and the valence band went upward. The number of photogenerated electron-hole pairs increased as the impurity levels appeared in the band gap. In addition, ZnO nanorods exhibited a smaller grain size and a rougher surface under the effect of Ru. Meanwhile, the RuO2 nanoparticles on the surface of ZnO nanorods acted as the electron-transfer channel, helping electrons transfer to the counter electrode and delaying the recombination of the electron-hole pairs. Specifically, the RuxZn1−xO/Ti electrodes with 9.375 mol% Ru exhibited the best PEC performance with a rhodamine B (RhB) removal rate of 97%, much higher than the combination of electrocatalysis (EC, 12%) and photocatalysis (PC, 50%), confirming the synergy of photoelectrocatalysis.

Exploring composite materials with ideal structures is an effective way to achieve synergy among different functional components. In this paper, a thermal decomposition method was adopted to prepared IrO2–CeO2-graphene/Ti composite electrodes. The influence of adding graphene on the composite material's electronic structure was analyzed by first-principles calculations, and its microstructure and electrochemical performance were also observed though various tests. The results indicated that coatings containing graphene exhibited a hierarchical porous structure, which could enlarge the specific surface area effectively. The band gaps of the IrO2–CeO2 composite oxides were filled by the energy level of C, which reduced the electron-transfer resistance. With amorphous CeO2 and the graphene acting as highly efficient ion-diffusion and electron-transfer channels respectively, the electrodes' charge storage performances were improved. The electrodes' specific capacitance values rose at first, then decreased as the graphene contents increased, reaching a maximum of 368 F g−1 when the content was 2 mg mL−1. However, adding graphene could harm the electrodes' cycling stability; excessive graphene could also encapsulate IrO2 nanoparticle and hinder contact with the electrolyte, thus reducing the electrodes' specific capacitances.

Making full use of low-energy photons and reducing photogenerated carriers' recombination rate have been considered important ways to raise photoelectrocatalysis (PEC) efficiency. In this study, Ir-doped ZnO PEC electrodes were prepared by thermal decomposition method, first principles calculations were used to study the effects of Ir content on the electronic structure and optical properties of IrxZn1-xO coatings, the PEC degradation mechanism of the IrxZn1-xO/Ti electrodes was also tentatively presented. The results indicated that with numbers of Zn atoms replaced by Ir atoms, impurity energy level appeared in ZnO band gap, which reduced the electron transition barriers and increased the number of photogenerated carriers. Besides, IrO2 nanoparticles covered on ZnO nanorods surface, acting as highly efficient electron transfer channels and electrocatalytic active sites, could separate photogenerated electron-hole pairs and enhance PEC performance effectively. PEC performance of IrxZn1-xO/Ti electrodes with different Ir contents under UV irradiation was evaluated by rhodamine B (RhB) removal rate. Compared with pure ZnO electrodes, IrxZn1-xO/Ti ones exhibited much stronger degradation capacity. Specifically, Ir0.09375Zn0.90625O/Ti electrodes showed the highest degradation rate of 99.4 %, and a relatively high rate of 95.2 % after working 100 h continuously, indicating its excellent long-term stability.

Enhancing the energy density and power density of the supercapacitor has long been the hot topic in the field of new energy storage devices, in which electrode materials including those for anodic and cathodic play a key role. This paper prepared IrO2–ZnO nanoelectrode by thermal decomposition method, analyzed the relationship between the capacitive properties and structures of the electrodes in detail. The results shown that electrodes prepared at 370 °C exhibited an intensive redox action, relatively low charge transfer resistance and high capacitance value of 487 F g−1 due to the plenty active sites provided by its large specific surface area and IrO2–ZnO nano-particles distributed evenly in the amorphous structures. A binder-free asymmetric supercapacitor working in H2SO4 solution was assembled with RuO2–MoO3/Ti and IrO2–ZnO/Ti as cathodic and anodic respectively. It exhibited energy densities of 10.9 W h kg−1 and 2.1 W h kg−1 when the power density was 26.7 W kg−1 and 267.5 W kg−1 respectively. Furthermore, it’s the first time to detect energy density and power density in acid solution of RuO2–MoO3/Ti cathode without using of binding materials, which is likely to become an important method to produce such pseudocapacitor in an industrial scale.