Abstract
As a representative photocatalyst for photoelectrochemical solar water splitting, TiO2 has been intensively studied but most researches have focused on the rutile and anatsase phases because brookite, another important crystalline polymorph of TiO2, rarely exists in nature and is difficult to synthesize. In this work, hydrogen doped brookite (H:brookite) nanobullet arrays were synthesized via a well-designed solution reaction for the first time. H:brookite shows highly improved PEC properties with excellent stability, enhanced photocurrent, and significantly high Faradaic efficiency for overall solar water splitting. To support the experimental data, ab initio density functional theory calculations were also conducted. At the interstitial doping site that has minimum formation energy, the hydrogen atoms act as shallow donors and exist as H+. which has the minimum formation energy among three states of hydrogen (H+. H0, and H−). The calculated density of states of H:brookite shows a narrowed bandgap and an increased electron density compared to the pristine brookite. The combined experimental and theoretical results provide frameworks for the exploration of the PEC properties of doped brookite and extend our knowledge regarding the undiscovered properties of brookite of TiO2.
Highlights
Over the past few decades, photoelectrochemical (PEC) hydrogen generation through solar water splitting has drawn increasing attention as a promising way of renewable energy production[1,2,3,4]
The present study is designed to determine the effect of hydrogen doping in the brookite via the combined analysis of experiments and density functional theory (DFT) theory
Because brookite is difficult to synthesize, no single study has previously reported the properties of doped brookite
Summary
Over the past few decades, photoelectrochemical (PEC) hydrogen generation through solar water splitting has drawn increasing attention as a promising way of renewable energy production[1,2,3,4]. The development of heterostructures of TiO2 with a narrow band gap QD or dye, which can assist visible light absorption, has some obstacles, such as complicated fabrication processes that require several steps and instability of QD or dye (which can be decomposed and corroded in solution reactions). Another approach to utilize visible light is anion/metal doping of TiO2 to narrow the bandgap of the photoelectrode material. This work is the first study reporting the preparation and enhanced PEC overall solar water splitting properties of hydrogen doped brookite nanostructure. The combined experimental and theoretical analysis results suggest that H:brookite TiO2 has a promising potential as a efficient photoanode for overall solar water splitting
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