Abstract
WO3 vertical plate-like arrays provide a direct pathway for charge transport, and thus hold great potential as working electrodes for photoelectrochemical (PEC) water splitting. However, surface recombination due to surface defects hinders the performance improvement. In this work, WO3 vertical plate-like arrays films with HfO2 passivation layer were fabricated via a simple dip-coating method. In the images of transmission electron microscope, a fluffy layer and some small sphere particles existed on the surface of WO3 plate. X-ray photoelectron spectroscopy (XPS) showed a higher concentration of Hf element than the result of energy-dispersive X-ray spectroscopy (EDX), which means that HfO2 is rich on the surface of WO3 plates. A higher photocurrent under visible light irradiation was gained with surface passivation. Meanwhile, the results of intensity modulated photocurrent spectrum (IMPS) and incident photon to current conversion efficiency (IPCE) indicate that HfO2 passivation layer, acting as a barrier for the interfacial recombination, is responsible for the improved photoelectrochemical performance of WO3 vertical plate-like arrays film.
Highlights
Photoelectrochemical (PEC) water splitting is a significant technology for relieving the energy crisis and environmental issues [1]
Because the WO3 particles were covered with HfO2 before the film was prepared, and the charge transport in WO3 nanoparticles film occurred via a random walk in a trap-limited diffusion process, a certain amount of photo-generated electrons transferred to fluorine-doped tin oxide (FTO) through HfO2 layer, and the HfO2 might have acted as a compact layer when it was inserted between the interfaces of FTO and WO3 (Scheme 1)
We report a simple dip-coating and annealing method to synthesize HfO2 passivation layer loaded on the surface of WO3 vertical plate-like arrays
Summary
Photoelectrochemical (PEC) water splitting is a significant technology for relieving the energy crisis and environmental issues [1]. Because the WO3 particles were covered with HfO2 before the film was prepared, and the charge transport in WO3 nanoparticles film occurred via a random walk in a trap-limited diffusion process, a certain amount of photo-generated electrons transferred to fluorine-doped tin oxide (FTO) through HfO2 layer, and the HfO2 might have acted as a compact layer when it was inserted between the interfaces of FTO and WO3 (Scheme 1). Scheme of the structures of WO3 and HfO2/WO3 films It is easy for the photogenerated electrons to recombine with photo-generated holes at the surface defect points of the WO3 plates. In this paper, we reported a dip-coating method to load HfO2 on the surface of WO3 vertical plate-like arrays. The influence of HfO2 passivation layer on the photoelectrochemical performance of WO3 is studied elaborately using several methods
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