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Mission of our group
Mission of our group
We have developed various spectroscopic and microscopic techniques to study the mechanism of photo-induced processes. We seek to control photo-generated charge carriers and photo-excited molecules at surfaces or interfaces or even in a micro-reactor. Our interests cover photocatalysis, photovoltaics, photofunctional liquid crystal and polymer. We utilize statistical data analysis for extracting big data obtained from spectroscopy and imaging.
News
News
2025/8/31-9/5 Prof. Katayama gave an invited talk at Optics of Liquid Crystals 2025, Kaohsiung, Taiwan. The title of the talk is "Illumination-Induced Solute Uptake in Liquid Crystal Droplets: The Role of Cyanobiphenyl-type Excimers."
2025/8/28-30 G-LAMP Symposium on Renewable Energy Technologies, Seoul, Korea was held. Prof. Katayama gave an invited talk, and seven members had poster presentations..
S. Fujiwara and M. Hosoya won the poster prizes out of the five winners.
Manami Hosoya
"Development of Wavelength Selective pot-PEIS Measurement and its Applications to Photocatalytic Water Splitting"
Shinichi Fujiwara
"Machine Learning Analysis of the Photocurrent–Voltage Curve directly from Scanning Electron Microscopy Images of α–Fe2O3"
2025/6/25-29 Visit to Donghua University and Lecture at 2nd New Energy Materials Industry Innovation Conference, Ningbo, China
Hosted by Prof. Qi Xiao and Prof. Xiaopeng Li at Donghua University, Katayama gave a lecture at Donghua Univeristy at Shanghai,
"Pattern-illumination time-resolved phase microscopy and mechanistic study on photocatalytic and photovoltaic materials"
In 2nd NEMIIC,
"Machine learning combined with analytical chemistry data to optimize materials: photoelectrochemical water splitting as an example"
Prof. Yamauchi at Kyushu Univ and Prof. Um, Handon at Kangwon National Univ. joined together.
2025/6/25 The 1st International G-LAMP Symposium on Renewable Energy Technologies has been announced!
Our former assistant professor, Prof. W. Y. Sohn will organize an international conference under the G-LAMP program. 7 members and I will give a talk there.
2025/5/31-6/1 第85回分析化学討論会（松山）で信岡，林，片山が発表しました。
“光触媒水分解材料の分析化学データを利用した機械学習的材料最適化（２）”
片山建二
“光触媒水分解材料の分析化学データを利用した機械学習的材料最適化（３）－溶液堆積法で作成するヘマタイト光アノード電極溶液の最適化”
林和麿
“機械学習を用いた水分解用酸化ニッケル電極性能の作成条件からの予測”
信岡春香
旧友の馬渡先生（早稲田大）のグループと懇親会を行いました。
2025/5/21-24 Visit to Chungbuk National University Again!
We visited Prof. Sohn's group at Chungbuk National University (CBNU) in Cheongju again to collaborate on a project and hold a workshop. Prof. Pan's group from the University of Hyogo also visited. Together, we performed a photoelectrochemical study on BiVO₄. Many of the younger students knew each other and mingled. The workshop was held in a café with a beautiful, huge garden. Two of our group members gave presentations, with Katayama talking about our recent work on machine learning.
"Machine Learning Combined with Analytical Sciences to Optimize Photoelectrochemical Water Splitting"
Kenji Katayama
"Observation of the Charge Carrier Dynamics of BiVO4 Photoanodes Synthesized by Three Types of Fabrication Methods by Pattern Illumination Time-resolved Phase Microscopy"
Yuki Nakatsukasa
"Predicting Nickel Oxide Electrode Performance for Water Splitting from Preparation Conditions Using Machine Learning"
Haruka Nobuoka
2025/4/17 New Paper Accepted
2025/4/26 Paper Online
"Direct Visualization of Interfacial Charge Transfer in CsPbBr₃ Perovskite Solar Cells Using Pattern-Illumination Time-Resolved Phase Microscopy"
authored by Tatsuki Ito and Kenji Katayama accepted in ACS Applied Materials & Interfaces, DOI:10.1021/acsami.5c02923
With our home-built PI-PM method, we can differentiate the electron and hole dynamics on a microscopic level. Furthermore, only the charge trapping to surface states and their following recombination can be observed, different from transient absorption or time-resolved phosphorescence. In this study, doping TiO₂ with Li or Pt as an electron transport layer significantly enhances charge separation, with Pt-doped TiO₂ showing the longest charge carrier lifetimes and lowest recombination rates. Hole transport layers (P3HT and Spiro-OMeTAD) play a critical role in hole transport efficiency, with P3HT outperforming Spiro-OMeTAD.
2025/4/16 Our paper is one of the selection of "Light-matter Interaction at the Nano and Molecular Scale"
"Cocatalyst Activity Mapping for Photocatalytic Materials Revealed by the Pattern-Illumination Time-Resolved Phase Microscopy"
Y. Egawa, K. Kawaguchi, Z. Pan, and K. Katayama
Journal of Chemical Physics, 160, 164705 (2024)
2025/3/26-29
日本化学会第105春季年会にて3名のメンバーが発表しました。（松沢、綾部、松本）
“Influence of cocatalysts on photo-excited charge carrier dynamics in titanium oxide photocatalysis observed using Pattern-Illumination Time-resolved Phase Microscopy”
Kana Matsumoto
“Feature extraction of microwave annealed hematite photoanodes using the factor analysis of machine learning model”
Kaori Matsuzawa
“Neural Network-Based Analysis of the Correlations Between Photoelectrode Performance, Microscopic Images, and UV-Vis Spectra for BiVO4 Photoanode Electrodes”
Hazuki Ayabe
2025/3/17-18 Sohn's group (Chungbok National University) visit
Prof. Sohn and 3 members of his group visited us to work on the collaboration research of the charge carrier dynamics measurements using the pattern-illumination time-resolved phase microscopy (PI-PM). We had a welcome party for them.
2025/3/4-5
高知大学にて森勝伸先生の世話のもと、集中講義を行いました。
セミナー発表を行いました。
「研究段階から使える機械学習と分析科学データを組み合わせた材料最適化」―光電気化学水分解材料を例に―”
片山建二
2025/1/24 New Paper Accepted
2025/2/3 Paper Online
"Charge Carrier Dynamics in Mixed-Dimensional CsPbBr3 Perovskites: Transition from 2D to 3D Architectures"
authored by Tatsuki Ito, Kenji Katayama in Journal of Physical Chemistry C, DOI: 10.1021/acs.jpcc.5c00206
The electron accumulation in a 3D perovskite microcrystal surrounded by 2D nanocrystals accumulating holes after photoexcitation could be imaged by pattern illumination time-resolved phase microscopy. We systematically studied the charge carrier behavior on 2D/3D CsPbBr3 by precursor control.
2025/1/28 Collaboration Paper Online
"Enhancement of the Photoelectrochemical Performance of Bismuth Vanadate (BiVO4) Photoanode by Building a W:BiVO4/Mo:BiVO4 Homojunction"
authored by Kim, Ji Hyun; Jeong, Seung Hyeon; Hong, Aram; Pan, Zhenhua; Katayama, Kenji; Sohn, Woon Yong in Bulletin of the Korean Chemical Society, DOI: 10.1002/bkcs.12943
2025/1/13 New Paper Accepted
2025/1/27 Paper Online
"Insight into Charge Transport Behaviors in Hematite Photoanodes via Potential-Dependent Impedance Spectroscopy and Machine Learning"
authored by Hiroomi Shoda, Zhenhua Pan, Woon Yong Sohn, Kenji Katayama in ACS Applied Materials & Interfaces, DOI:10.1021/acsami.4c19865
We unveiled the critical charge transport mechanisms, accelerating material optimization for solar water splitting. By combining Shapley Additive Explanations (SHAP) and advanced analytical data, our study identifies how shallow and deep defect states dictate electron and hole transport in hematite photoanodes.
2025/1/22 Collaboration Paper Online
"Hydrogen peroxide photosynthesis from water and air using a scaled-up 1-m2 flow reactor"
authored by Xiaoshan Zheng, Rito Yanagi, Zhenhua Pan, Chong Zhou, Tian Liu, Baoliang Chen, Kenji Katayama, Shu Hu, Chiheng Chu in Chem Catalysis, DOI:10.1016/j.checat.2024.101238
A large-scale demonstration for H2O2 generation by BiVO4 including polymer film.
2025/1/17-18 5th NCU/CHUO Chemistry Workshop
Dr. Nagai and Prof. Katayama gave talks at the workshop. We had a warm welcome from the NCU members.
"Pattern-illumination time-resolved phase microscopy and mehanistic study on photocatalytic materials"
Kenji Katayama
"Machine learning x Analytical data optmization for photocatalytic materials
Yuya Nagai, Kenji Katayama
2025/1/7 Nagai's defense for PhD
A PhD candidate, Mr. Nagai has successfully completed the final presentation, "“機械学習と分析化学データを用いたデータ駆動的材料作製法による 光半導体電極の開発” (Development of photoelectrochmical electrodes by the data-driven approach using the combination of machine learning and analytical data) for his Ph.D. defense. Prof. Iwase of Meiji University (expert in photocatalytic water splitting), Prof. Higushi (expert in machine learning and data science), Prof. Ueno (expert in analytical chemistry), and Prof. Mori (expert in quantum chemistry) evaluated his thesis.
2024/12/10-23 Long-term visit
Prof. Vincent Ko at City University of Hong Kong visited our group from Dec. 10-23. He gave lectures on “Design of Luminescent Transition Metal Complexes and Their Application as Phosphorescent Materials and Photocatalysts” and “Stimuli-Responsive Luminescent Materials”. Thank you for giving us good insights.
2024/11/12-15 International collaboration workshop in CNBU, Korea
We had a collaboration workshop with Prof. Sohn at Chungbuk National University. Katayama gave a lecture on the PI-PM method for an hour, and a student seminar was held, and our members, Mr. Fujiwara and Ms. Hosoya gave talks on their research. They arranged a happy dinner and excursion for us.
2024/11/11 Collaboration Paper Online
"Spatially selective actuation of liquid-crystalline polymer films through two-photon absorption processes"
authored by Toru Ube, Shota Sasaki, Kenji Katayama, Hikaru Sotome, Hiroshi Miyasaka, Ryota Mizutani, Kenji Kamada & Tomiki Ikeda in Nature Communications, 15, 9430 (2024).
Dr Ube from the Ikeda group has published a paper in Nature Communications and I am happy to be part of it. He has demonstrated two-photon actuation of a liquid crystalline polymer that includes an azobenzene moiety. The two-photon induced process expands the versatility of wavelength selection, positions and bending direction.
2024/10/24 International collaboration work will be started!
Prof. Sohn from Chungbok National University (former assistant professor of our group) visited us to start an international collaboration through the G-lamp project supported by the Korean government. The G-LAMP project is a national initiative aimed at improving the basic research capabilities of universities and producing innovative research results to train world-class researchers.
2024/10/25 Paper Online
2024/10/14 Paper Accepted
"Tailoring Hematite Photoanodes for Improved PEC Performance: The Role of Alcohol Species Revealed by SHAP Analysis"
authored by Takumi Idei, Yuya Nagai, Zhenhua Pan and Kenji Katayama in ACS Omega, DOI: 10.1021/acsomega.4c08633
One of the big challenges of using machine learning for material development is that you can only use it to 'interpolate', meaning that you can make a material within the predicted range and not go beyond an unexpected range. To overcome "interpolation" and realise "extrapolation", we have tried to develop a new strategy using an original SHAP analysis and a new SHAP analysis.
Machine learning models are combined to improve PEC performance by introducing a new type of SHAP analysis, called operational SHAP analysis, which represents the dependence of SHAP values on experimental operations. Linking the experimental operations and the dominant factors for determining the performance could suggest the direction of the promising experimental operation, beyond "extrapolation".
2024/10/4 Visitor
Dr. Han Fu Dongua , a postdoctoral fellow at Arizona State Univ, visited us to discuss the possible collaboration of the photocatalytic water splitting studies.
2024/10/3 Paper Online
2024/9/25 Paper Accepted
"Illumination-Induced Solute Uptake in Liquid Crystal Droplets: The Role of 5CB Excimers"
authored by Haruka Kido, Hinako Kusaki, Yota Sakai, Tomiki Ikeda and Kenji Katayama in Langmuir, DOI: 10.1021/acs.langmuir.4c03046
It has taken many years to get this paper published. Many generations of students have worked on this issue, and finally we found out the real reason why this movie happened. No one, except Prof. Ikeda, would expect that the uptake and accumulation of solutes in a droplet by light was caused by the excimer excitation of the 5CB liquid crystal.
MovieS1_5CB_droplet_SDS_p-nitrophenol.mp4Events
Events
2025/9/22-25
第76回コロイドおよび界面化学討論会, Chiba, Japan
P-19 シアノビフェニル系液晶液滴の紫外光照射に伴う変形現象
天利優太、木戸遥、片山建二
2025/9/10-12
2025年日本液晶学会討論会, Kyoto, Japan
PA-01 シアノビフェニル系液晶液滴の紫外光照射に伴う変形現象
天利優太、木戸遥、片山建二
2025/9/8-9/12
9th International Conference on Semiconductor Photochemistry, Madrid, Spain
Keynote lecture
"Material Optimization by Combination of Machine Learning and Analytical Data in the Research and Development of Photocatalytic Materials"
Kenji Katayama
"Pattern-illumination Time-resolved Phase Microscopy and its Applications for Photocatalytic and Photovoltaic Materials"
Kenji Katayama
2025/8/31-9/5
Optics of Liquid Crystals 2025, Kaohsiung, Taiwan
Invited lecture
"Illumination-Induced Solute Uptake in Liquid Crystal Droplets: The Role of Cyanobiphenyl-type Excimers"
Kenji Katayama
2025/8/28-8/30
G-lamp international conference, Seoul, Korea
Invited lecture
"Material Optimization by Combination of Machine Learning and Analytical Data in the Development of Photocatalytic Materials"
Kenji Katayama
Posters
Haruka Nobuoka
"Machine Learning Utilization for Predicting the Performance of Nickel Oxide Electrocatalysts for Water Splitting "
Manami Hosoya
"Development of Wavelength Selective pot-PEIS Measurement and its Applications to Photocatalytic Water Splitting"
Shinichi Fujiwara
"Machine Learning Analysis of the Photocurrent–Voltage Curve directly from Scanning Electron Microscopy Images of α–Fe2O3"
Yuki Nakatsukasa
"Observation of the Charge Carrier Dynamics of BiVO4 Photoanodes Synthesized by Three Types of Fabrication Methods by Pattern Illumination Time-resolved Phase Microscopy"
Kazuma Hayashi
"Optimization of the Solution deposition condition for hematite preparation by using machine learning "
Kana Matsumoto
"Influence of AI doping on photo-excited charge carrier dynamics in strontium titanate photocatalysts observed using Pattern-IIIumination Time-resolved Phase Microscopy"
Kaori Matsuzawa
"Machine learning analysis of photoelectrode properties fabricated with mocrowave annealing "
2025/6/26-6/28
2nd New Energy Materials Industry Innovation Conference, Ningbo, China
Invited lecture
"Machine learning combined with analytical chemistry data to optimize materials: photoelectrochemical water splitting as an example"
Kenji Katayama
2025/5/31-6/1
第85回分析化学討論会
6/1 E1001 9:00-9:15
“光触媒水分解材料の分析化学データを利用した機械学習的材料最適化（２）”
片山建二
6/1 E1002 9:15-9:30
“光触媒水分解材料の分析化学データを利用した機械学習的材料最適化（３）－溶液堆積法で作成するヘマタイト光アノード電極溶液の最適化”
林和麿，出井拓己，永井優也，片山建二
6/1 E1003 9:30-9:45
“機械学習を用いた水分解用酸化ニッケル電極性能の作成条件からの予測”
信岡春香，林祐太，永井優也，片山建二
2025/5/21-24
Research workshop at Chungbok National University
"Machine Learning Combined with Analytical Sciences to Optimize Photoelectrochemical Water Splitting"
Kenji Katayama
"Observation of the Charge Carrier Dynamics of BiVO4 Photoanodes Synthesized by Three Types of Fabrication Methods by Pattern Illumination Time-resolved Phase Microscopy"
Yuki Nakatsukasa and Kenji Katayama
"Predicting Nickel Oxide Electrode Performance for Water Splitting from Preparation Conditions Using Machine Learning"
Haruka Nobuoka, Yuta Hayashi, Yuya Nagai, Kenji Katayama
2025/3/26-29
日本化学会第105春季年会
3/28, C401-3pm-09, 2:30 PM - 2:40 PM
“Influence of cocatalysts on photo-excited charge carrier dynamics in titanium oxide photocatalysis observed using Pattern-Illumination Time-resolved Phase Microscopy”
Kana Matsumoto, Yuki Nakatsukasa, Yuta Egawa, Kenji Katayama
3/27, C403-2am-04, 9:30 AM - 9:40 AM
“Feature extraction of microwaveannealed hematite photoanodes using the factor analysis of machine learning model”
Kaori Matsuzawa, Yuya Nagai, Kenji Katayama
3/27 A405-2am-06, 10:20 AM - 10:30 AM
“Neural Network-Based Analysis of the Correlations Between Photoelectrode Performance, Microscopic Images, and UV-Vis Spectra for BiVO4 Photoanode Electrodes”
Hazuki Ayabe, Shinichi Fujiwara, Yuta Hayashi, Kenji Katayame
2025/3/5
高知大学セミナー
「研究段階から使える機械学習と分析科学データを組み合わせた材料最適化」―光電気化学水分解材料を例に―”
片山建二
2024/1/17-18
5th NCU/CHUO Chemistry Workshop, National Central University (Taoyuan, Taiwan)
10:55-11:15
"Pattern-illumination time-resolved phase microscopy and mehanistic study on photocatalytic materials"
Kenji Katayama
11:35-11-55
"Machine learning x Analytical data optmization for photocatalytic materials
Yuya Nagai, Kenji Katayama
2024/1/7
博士公聴会
13:00-14:00 後楽園キャンパス3号館3301号室
“機械学習と分析化学データを用いたデータ駆動的材料作製法による 光半導体電極の開発”
永井優也
2024/12/10-23
Visit of Prof. Ko, Chi Chiu Vincent, City University Hong Kong
12/12 (Thu)
“Design of Luminescent Transition Metal Complexes and Their Application as Phosphorescent Materials and Photocatalysts”
12/17 (Tue)
“Stimuli-Responsive Luminescent Materials”
2024/11/12-15
Collboration seminar with Chungbuk National University, Cheongiu, Korea
“Pattern-illumination Time-resolved Phase Microscopy and its Applications for Photocatalytic and Photovoltaic Materials”
Kenji Katayama
“Convolutional Neural Network Prediction of the Photocurrent-Voltage Curve directly from Scanning Electron Microscopic Image for BiVO4 and α-Fe2O3”
S. Fujiwara, Y. Hayashi, Y. Nagai, Z. Pan, and K. Katayama
“Potential dependent photoelectrochemical impedance spectroscopy and its applications to photocatalytic water splitting”
M. Hosoya, T. Idei, and K. Katayama
2024/10/21
光機能材料研究会25周年記念・第99回講演会 online
「研究段階から使える機械学習と分析科学データを組み合わせた材料最適化」―光電気化学水分解材料を例に―”
片山建二
2024/9/4-6
10th Japanese-Italian Workshop on Liquid Crystals, Miyazaki, Japan
9/5 C6
“Excimer-Driven Molecular Intake in Liquid Crystalline Droplets”
Kenji Katayama, Haruka Kido, Hinako Kusaki, and Yota Sakai
Poster P19
“Formation of topological defects at liquid/liquid crystal interfaces in micro-wells controlled by surfactant and ligh”
Takuro Yoshimura, Kenji Katayama
Poster
“Illumination-induced Solute Uptake into Liquid Crystal Droplets by excimer state of 5CB”
Haruka Kido, Kenji Katayama
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