One-Dimensional p-ZnCo₂O₄/n-ZnO Nanoheterojunction Photoanode Enabling Photoelectrochemical Water Splitting

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.

Reinforcement of Visible-Light Harvesting and Charge-Transfer Dynamics of BiVO4 Photoanode via Formation of p–n Heterojunction with CuO for Efficient Photoelectrocatalytic Water Splitting

“…The formation of the IEF at the interface restricts the further movement of the electrons and causes band bending in the BiVO 4 (upward) and CuO (downward), and it is shown in Figure b . Upon light illumination, this IEF quickly drives electrons to the CBM of BiVO 4 and holes to the VBM of CuO, and thus, the IEF effectively separates the electrons and holes . When light falls on the BiVO 4 /CuO electrode, both the BiVO 4 and CuO undergo charge separation.…”

Sulfate-Functionalized Core–Shell ZnO/CdS/Ag2S Nanorod Arrays with Dual-Charge-Transfer Channels for Enhanced Photoelectrochemical Performance

“…Effective utilization of solar energy is a sustainable approach to alleviating the coming crisis of fossil energy depletion and global warming. − In addition to photovoltage cells, photoelectrochemical (PEC) water splitting is a potential technology for the production of hydrogen energy by solar energy conversion . To achieve excellent PEC performance, suitable semiconductor materials as photoelectrodes are of crucial importance in terms of sufficient light-harvesting, efficient charge transport from bulk to surface, and energetic surface reaction. − Up to date, some oxide semiconductors such as TiO 2 , Fe 2 O 3 , and ZnO have been extensively researched as photoelectrode materials for PEC water splitting. Among these photoelectrode materials, ZnO is a promising semiconductor due to its high electron mobility, low cost, and nontoxic. , However, with a big band gap of about 3.3 eV, ZnO only possesses a small light-absorption range .…”

Integrated Photovoltaic Charging and Energy Storage Systems: Mechanism, Optimization, and Future

“…Reproduced with permission. [ 80 ] Copyright 2021, American Chemical Society. b) Schematic image set of fabrication steps for the Ga 2 O 3 / Cu 2 O‐based photoanode and photographic image of the sample.…”

“…[77][78][79] For example, Maity et al formed a p-n junction through the integration between p-ZnCo 2 O 4 and n-ZnO nanorods, a type II-like band alignment would occur, which accelerated charge separation and transfer, significantly reducing the photogenerated electron-hole pair compound and improve stability (Figure 5a). [80] Kim et al used electrochemical deposition to deposit an Au layer on a p-n junction composed of Cu 2 O/Ga 2 O 3 , and then formed a Ni-based cocatalyst. [78] This enables more photogenerated hole charges to be transported to the electrolyte, significantly reducing the overpotential and improving the photoactivity (Figure 5b).…”

“…Figure 5. a) ZnO/ZnCo 2 O 4 nanoheterojunction photoanode;The probable photocarrier generation and transfer mechanism; chronoamperometry j-t) plots at 0 V versus Ag/AgCl. Reproduced with permission [80]. Copyright 2021, American Chemical Society.…”