Vertically aligned one-dimensional ZnO/V2O5 core–shell hetero-nanostructure for photoelectrochemical water splitting

Abstract

• Vertically aligned 1D ZnO/V 2 O 5 core-shell nanoheterostructure photoanode for PEC water splitting application. • Facilitating kinetics of charge generation, separation and transfer as well as lower e-h pairs recombination rate. • The staggered band level alignment between ZnO and V 2 O 5 . • Optimal electrochemically active surface area with less recombination sites owing to the 1D core-shell structure. The vertically aligned one-dimensional (1D) core–shell structure can maximize the exposure and use of the functionally active surface while maintaining the geometric effects caused by the underlying structure. Herein, we have fabricated 1D vertically aligned ZnO/V 2 O 5 core–shell hetero-nanostructure nanorod arrays (NRs) for photoelectrochemical (PEC) water splitting. ZnO/V 2 O 5 NRs were prepared through the hydrothermal growing of ZnO NRs and then radio frequency (RF) magnetron sputtering deposition of V 2 O 5 for 300, 600 and 900 s. The photocurrent density of ZnO/V 2 O 5 -based photoanodes was gradually increased with the sputtering time, reaching the maximum value of 1.21 mA/cm 2 at 1.23 V vs. reversible hydrogen electrode (RHE) for ZnO/V 2 O 5 -600, whereas for pure ZnO-based photoanode was 0.42 mA/cm 2 . The incident photon to electron conversion efficiency (IPCE) of ZnO/V 2 O 5 -600 evaluated to be 82.3% which was 2.3 times higher than that of ZnO (36.4%). The improved PEC performance of ZnO/V 2 O 5 -600 is because the core–shell structure with a moderate thickness of the V 2 O 5 layer has the extremely high carrier density, largest electrochemically active surface area (ECSA), largest carrier density, lowest charge recombination rate, and the longest lifetime of e-h pairs due to the formation of the staggered gap junction. This study provides an effective way to design and fabrication of hetero-nanostructures for high-efficiency photoelectrodes. With the low bandgap of V 2 O 5 and the staggered band offset, the photogenerated carriers in the ZnO/V 2 O 5 can be enhanced and facilitated the separation and tansport at the same time.