One-Dimensional p-ZnCo<sub>2</sub>O<sub>4</sub>/n-ZnO Nanoheterojunction Photoanode Enabling Photoelectrochemical Water Splitting
Dipanjan Maity, Keshab Karmakar, Debashish Pal, Soham Saha, Gobinda Gopal Khan, Kalyan Mandal
Abstract
This work demonstrates the photoelectrochemical (PEC) water splitting activity of a one-dimensional n-ZnO/p-ZnCo2O4 nanoheterojunction photoanode synthesized by using the chemical bath deposition and electrodeposition methods. The nanoheterojunction photoanode exhibits an improved solar light-harvesting performance. The type-II analogous band alignment occurs because of p–n junction formation between p-ZnCo2O4 and n-ZnO nanorods (NRs), which accelerates the charge separation and transfer, significantly reducing the photogenerated electron–hole pair recombination. The ZnCo2O4 surface overlayer also passivates the surface states in ZnO, resulting in a remarkable reduction in photocarrier recombination. Additionally, the p-ZnCo2O4 shell layer acts as the oxygen evolution reaction (OER) catalyst to influence the PEC reactions at the electrode/electrolyte interface, boosting the charge transfer process and water oxidation reaction kinetics. Overall, an innovative nanoheterojunction photoanode is constructed to improve the PEC water oxidation of ZnO NRs by incorporating p-ZnCo2O4, which acts both as an OER catalyst and a p-type light-harvesting semiconductor.