Photocatalysts enable the use of sunlight to drive chemical reactions. Upon absorbing light, they produce electrons and holes, which then initiate reactions such as hydrogen production and CO2 conversion. PTOF stands out among these materials due to its ability to absorb visible light and its resistance to oxidative degradation.
Led by Professors Kazuhiko Maeda of Science Tokyo and Osamu Ishitani of Hiroshima University, the research team created highly porous PTOF nanoparticles using a microwave-assisted hydrothermal process. Published online July 09, 2025 and in the July 18 issue of ACS Catalysis, their work offers a blueprint for scalable, green photocatalytic material design.
"The synthesis method established in this study enables world-leading photocatalytic performance for H2 production and the conversion of CO2 into formic acid among oxyhalide photocatalysts, using an environmentally friendly process," said Maeda.
The key to their approach lies in particle size and morphology control. By minimizing particle size, the team reduced the travel distance for photogenerated charge carriers, lowering recombination rates. Unlike typical methods that risk structural defects, their technique preserved catalytic integrity.
The team tested different water-soluble titanium complexes-based on citric, tartaric, and lactic acids-as titanium sources, alongside lead nitrate and potassium fluoride. The conventional titanium chloride precursor yielded larger, less porous particles (~0.5-1 um, surface area ~2.5 m2g-1), whereas the optimized method produced nanoparticles under 100 nm with surface areas around 40 m2g-1.
Catalytic testing showed remarkable results. Citric acid-derived PTOF achieved a sixtyfold increase in hydrogen production compared to the TiCl4-based sample, with a quantum yield of 15% at 420 nm. For CO2-to-formic acid conversion, tartaric acid-derived PTOF reached a 10% quantum yield when combined with a molecular ruthenium photocatalyst-both values setting new performance records for this class of materials.
Despite their smaller size correlating with lower charge mobility, the proximity of surface reaction sites enhanced overall photocatalytic efficiency. This highlights how nanostructuring can overcome typical limitations in photocatalyst design.
The team's microwave-assisted synthesis offers a scalable, low-temperature pathway for fabricating high-performance photocatalysts. "This study underscores the importance of controlling the morphology of oxyhalides to unlock their full potential as photocatalysts for artificial photosynthesis. These findings are expected to significantly contribute to the development of innovative materials that help address global energy challenges," Maeda concluded.
Research Report:Mesoporous Oxyhalide Aggregates Exhibiting Improved Photocatalytic Activity for Visible-Light H2 Evolution and CO2 Reduction
Related Links
Institute of Science Tokyo
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