Novel nanostructured photoanode hydrothermally prepared at 160°C, followed by 500°C calcination

A new study led by Prof. Tianyou Peng (College of Chemistry and Molecular Sciences, Wuhan University) and Associate Prof. Peng Zeng (School of Food and Pharmaceutical Engineering, Zhaoqing University) describes how a novel nanostructured WO₃-based photoanode was hydrothermally prepared at 160°C followed by 500°C calcination.

In addition, the influence mechanism of hydrazine hydrate and In³⁺-doping on the microstructure, photoelectrochemical behavior, electronic band structure and work function of WO₃ photoanode was studied.

The work is published in the journal Science China Chemistry.

The experiment results show that the photocurrent density and stability of the nanostructured WO₃ photoanode are closely related to its microstructure, morphology and electronic band structure, whereby the introduction of hydrazine hydrate as texture regulator in the hydrothermal reaction solution leads to the formation layered WO₃ film stacked by (020) facet-exposed nanosheets with ~300 nm length (along the [200] direction) and ~150 nm width (along the [002] direction).

This increases the specific surface area and reactive sites to promote the charge transfer and separation; In³⁺-doping optimizes the electronic band structure of WO₃, resulting in negatively shifted flat band potential and reduced work function to enhance the driving force of OER.

Compared to In³⁺ ions, the introduction of hydrazine hydrate has more significant improvement effects on the photocurrent density, applied bias photon-to-current efficiency (ABPE), incident-photon-to-current conversion efficiency (IPCE), photoelectrochemical durability and Faraday efficiency for O₂ evolution.

Under the synergistic effect of hydrazine hydrate modification and In³⁺-doping, the OER performance of In³⁺-WO₃(N₂H₄) photoanode was significantly improved.

Under conditions of AM1.5G simulated sunlight illumination, Na₂SO₄ solution and 1.23 V vs. RHE, the In³⁺-WO₃(N₂H₄) photoanode constructed under the optimized conditions exhibited an IPCE of 38.6% (at 410 nm) and a photocurrent density of 1.93 mA cm^-2, which are 2.8 and 3.0 times that of the pure WO₃ photoanode, respectively.

This OER performance of In³⁺-WO₃(N₂H₄) is comparable to or even better than most reported WO₃-based photoanodes, indicating its practical application potential in PEC water splitting. This research provides a promising strategy to improve the PEC OER performance of nanostructured WO₃ photoanodes by altering their microstructure and introducing heteroatoms.