Electronic structure and enhanced photoelectrocatalytic performance of [Ru.sub.x][Zn.sub.1-x]O/Ti electrodes

Modification is one of the most important and effective methods to improve the photoelectrocatalytic (PEC) performance of ZnO. In this paper, the [Ru.sub.x][Zn.sub.1-x]O/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 [Ru.sup.4+] transferred into ZnO lattice and replaced a number of [Zn.sup.2+], 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 Ru[O.sup.2] 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 [Ru.sub.x][Zn.sub.i-x]O/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. Keywords: [Ru.sub.x][Zn.sub.1-x]O/Ti electrode; first-principles calculation; electric collector; photoelectric synergistic catalysis