Spiral-Growth-Induced Nanosteps on Layered Oxyhalide Photocatalysts Enhance Anisotropic Charge Separation for Visible-Light Water Splitting
Year: 2026
Type: preprint
Abstract: Layered mixed-anion compounds are promising photocatalysts for solar fuel production owing to their visible-light absorption and suitable band-edge positions. However, their two-dimensional crystal structures hinder the spatial separation of reduction and oxidation sites because both photogenerated electrons and holes predominantly migrate in-plane along the layered frameworks. In particular, in plate-like particles reflecting this layered structure, charge carriers must travel relatively long lateral distances. Here, we overcome this limitation for the first time by introducing step structures on the basal planes, which shorten the lateral carrier migration while spatially separating redox sites. Using the layered oxyhalide Bi 4 NbO 8 Cl as a model photocatalyst, nanoscale steps are formed on the basal planes of plate-like crystals via screw-dislocation-driven spiral growth during flux synthesis. Subsequent acid etching converts the basal planes from photogenerated electron-rich to hole-accumulating surfaces, as revealed by surface photovoltage spectroscopy, enabling preferential photodeposition of reduction cocatalysts onto the electron-rich nanosteps. This asymmetric cocatalyst loading promotes anisotropic charge separation, resulting in a 16-fold enhancement in the photocatalytic H 2 evolution rate compared to the untreated sample and achieving one of the highest apparent quantum efficiencies reported for layered oxyhalide photocatalysts. Furthermore, etched samples with nanosteps exhibit enhanced photocatalytic water oxidation under visible-light Z-scheme water splitting, demonstrating the effectiveness of this surface engineering for solar water splitting. This study establishes spiral-growth-induced step formation combined with surface etching as a new design strategy for controlling carrier flow in layered photocatalysts, unlocking their potential for solar energy conversion.
Source: ChemRxiv
Authors: Makoto Ogawa, Hajime Suzuki, Yi-Hao Chew, Mahya Salmanion, Rajesh Kandel, Osamu Tomita, Akinobu Nakada, Akira Yamakata, Frank E. Osterloh, Ryu Abe
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: green
Awards: Development of remarkable photocatalysts based on charge carrier dynamics, Development of highly efficient photocatalyst for water splitting by a high-speed search method, Engineering of Charge Transfer at the Heterojunction, Precise Control of Particle Morphology in Mixed-Anion Compounds for Enhanced Photocatalytic Activity
OpenAlex ID: W7211870954