Katayama Group, Chuo University

Spectroscopy and Photochemistry

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

"Robust methodology for PEC performance analysis of photoanodes using machine learning and analytical data"
authored by Moeko Tajima, Yuya Nagai, Zhenhua Pan and Kenji Katayama in Analyst 

Our machine learning & analytical chemistry strategy was summarized. This is our flagship paper of our recent works using ML optimization of photocatalytic materials.

"Subtraction descriptors in machine learning for optimizing the cocatalyst effect of cobalt phosphate on hematite photoanodes"
authored by Siyan Chen,  Yuya Nagai, Zhenhua Pan, Kenji Katayama in ACS Applied Materials & Interfaces DOI: 10.1021/acsami.4c06220

Our machine learning & analytical chemistry strategy harnesses our research to extract the cocatalyst effect only from the analytical data. By employing subtraction descriptors with/without cocatalysts, we've isolated and quantified only the impact of co-catalysts, Co-Pi, leading to unprecedented insights into photoelectrochemical performance enhancement. Explore how advanced analytical techniques combined with AI can revolutionize energy conversion materials.

Our group is looking for a candidate for the position of Assistant Professor (Jyokyo), starting April 1, 2025. See the application details.

Here is the application detail from JREC-IN.

"Unveiling Charge Carrier Dynamics in CsPbBr3 Perovskites with Hole Transport Layers: Insights from Pattern-Illumination Time-Resolved Phase Microscopy"
authored by Tatsuki Ito and Kenji Katayama in Journal of Physical Chemistry C, DOI:10.1021/1cs.jpcc.4c02438.

We can distinguish the electron and hole dynamics position by position and the sign of the refractive index change by our method. Therefore, we could clearly study the hole transfer dynamics at the perovskite/HTL interfaces. The result clearly indicates that the P3HT efficiently removes holes from the interface to the HTL.

"Experimental verification of double-four-ring-type aluminosilicate molecule as a single-source precursor for zeolite synthesis"
authored by Imaizumi, Akira; Ohnishi, Yurika; Nakada, Akinobu; Honda, Akinori; Matsumoto, Takeshi; Katayama, Kenji; Chang, Ho-Chol in Bulletin of the Chemical Society of Japan (BCSJ),  DOI: 10.1093/bulcsj/uoae060.

A new type of zeolite synthesis has been developed using a molecular precursor system. This is the work of a Ph.D. student in the Chang group, next door to our group.

"Combined Effect of Underlayer and Deposition Solution to Optimize the Alignment of Hematite Photoanodes"
authored by Takumi Idei, Zhenhua Pan, and Kenji Katayama in Langmuir, DOI:10.1021/acs.langmuir.4c00621.

We have found the highly stable hematite preparation by combining the TiO2 underlayer and ethanol including precursor solutions. The source of the performance enhancement was clarified by potential-dependent photoelectrochemical impedance spectroscopy, separating the origin of bulk electron transport and interfacial hole transfer.

I've joined the sign ceremony of the double degree with NCU for the master course students. It was a great experience meeting with many professors of NCU.

Chuo Univ News

"Cocatalyst Activity Mapping for Photocatalytic Materials Revealed by the Pattern-Illumination Time-Resolved Phase Microscopy"
authored by Yuta Egawa, Kei Kawaguchi, Zhenhua Pan, and Kenji Katayama in Journal of Chemical Physics, 160, 164705 (2024)

This paper describes the effectiveness of the PI-PM method for detecting active sites of co-catalysts. Two of the most important photocatalyst + cocatalyst combinations were studied; Pt/TiO2 and CoPi/hematite. Surprisingly, the active sites can be distributed on the micron scale, not on the nanoscale.

9 undergraduate, 7 graduate students and Assistant Professor Z. Pan have left our group. I appreciate your great efforts and contributions!

Dr. Pan will start his group at Hyogo University from this April.

"Pattern-illumination Time-resolved Phase Microscopy and its Applications for Photocatalytic and Photovoltaic Materials"
authored by Kenji Katayama in Physical Chemistry Chemical Physics, 2024, 26, 9783 - 9815 

This is a whole review paper on the PI-PM method, developed in the last 5-7 years. This paper covers from the principle to applications, providing the necessary knowedge and technology and its potential applications.

"Enhanced Photocatalytic Efficacy and Stability in Antibiotic Pollution Mitigation Using BiVO4 Nanoballs Encased in Ultrathin Polymeric g-C3N4 Nanocomposites under Visible Light Exposure"
authored by Muniyandi Govinda raj*, Ayyakannu Sundaram Ganeshraja, Kulandaivelu Kaviyarasan, Valdes Hector, Nalandhiran Pugazhenthiran, Kenji Katayama, Chandra Sekhara Theja Vaskuri, Aruljothy John Bosco, and Bernaurdshaw Neppolian in Journal of Physical Chemistry C, DOI: 10.1021/acs.jpcc.3c07599

Seven graduate students completed their final presentation for graduation.

We organized the 4th chemistry workshop between National Central University (NCU) and our department. We received 5 professors from NCU, and had active chemistry discussions. We are expecting the next workshop at NCU.

News in Chuo University

"Identification of the contributing factors to the photoelectric conversion efficiency for hematite photoanodes by using machine learning"
authored by Takumi Idei, Yuya Nagai, Zhenhua Pan and Kenji Katayama in ACS Applied Materials & Interfaces DOI:10.1021/acsami.3c11295

A combination strategy of various analytical data and machine learning (ML) has been applied to the "activity" of sluggish hematite electrodes. The descriptor selection provided us to pinpoint the origin of "inactivity", and can be recovered. 

"Convolutional Neural Network Prediction of the photocurrent−voltage curve directly from scanning electron microscopic image"
authored by Yuta Hayashi, Yuya Nagai, Zhenhua Pan and Kenji Katayama in Journal of Materials Chemistry A, 2023, 11, 22522-22532

Photocatalytic performance can be predicted with a single piece of an SEM image. A CNN was trained by the SEM images as an input and the JV curve as an output just by 28 samples, and the model could predict the JV curve with >95% accuracy.

We hosted three students from Universiti Teknologi Malaysia in the Sakura Science Program. They worked on the experiments on LC and time-resolved spectroscopy. Ito and Yoshimura took care of their experiments. 

"Formation of Topological Defects at Liquid / Liquid Crystal Interfaces in Micro-Wells Controlled by Surfactants and Light"
authored by Kenji Katayama, Takuro Yoshimura, Saki Yamashita, Hiroto Teratani, Tomoki Murakami, Hiroaki Suzuki, Jun-ichi Fukuda
is online at Soft Matter, 2023, 19, 6578 - 6588.

It took a lot of effort and time to create a topological defect platform that can be easily controlled by light and surfactant. This would be the first systematic study of the liquid/liquid crystal interface. We could make this possible by the strong cooperation with Prof. Fukuda at Kyushu Univ, theoretical calculations on LC alignment, and Prof. Suzuki at our univ, a professional on microfludic device.

Prof. A. Choodum, N. Tongtep, and K. Hashimoto at Prince of Songkla University visited our group to discuss the future collaboration on the decomposition of environmental hazardous materials and the data science applications. They also visited Prof. Funazukuri and Prof. Ueno groups for future collaboration on the sensor and recycling. 

We received a couple of students in the Sakura Science Program (JST) from National Central University (Taiwan). They experienced experiments about the photo-responsive liquid crystals and the hematite synthesis and its photochemical characterization. 

During their visit, Prof. Chun Guey Wu, who is a collaborator on the solar cell research, visited our group to discuss the further collaboration. 

Prof. F-K. Shieh at National Central University (Taiwan) visited our university to discuss the future friendship between chemistry departments, and looked around research groups. His expertise is MOF applications for photovoltaic applications, and discussed about our photocatalytic research.

"光応答液晶液滴の運動と機能"
"Photo-responsive Liquid Crystalline Droplets: Motion and Function"
片山建二
液晶 2023年4月号 p. 104

Prof. D. Wang at Boston College visited us to discuss the future collaboration of the diatomic catalysis and its collection of photo-excited holes  by our time-resolved imaging techinique. I've learned a lot of new progresses on his research.

Prof. J. Fukuda at Kyushu University visited us to discuss the theoretical calculation of the topological defects generated inside a microfluidic device, which will be submitted soon.

We will have a joint group meeting online with the members of Prof. Sohn, who was a former assistant professor in our group.

"Identification of Dominant Factors Contributing to Photocurrent Density of BiVO4 Photoanodes Using Machine Learning  "
authored by Kazuya Kobayashi, Yuya Nagai, Zhehua Pan, and Kenji Katayama
is online for Journal of Photochemistry and Photobiology A, 2023, 440, 114651.

Events

Poster
“Charge transfer processes at HTL/CsPbBr3 Cellsby Time-Resolved Pattern-illumination Phase Microscopy”
ITO Tatsuki; KATAYAMA kenji 

Poster
“Defect state identification contributing to the performance of α-Fe2O3 photoanode by Machine learning”
SHODA Hiroomi; NAGAI Yuya; PAN Zhenhua,; KATAYAMA Kenji

“Machine Learning Combined with Analytical Sciences to Optimize Photocatalytic Materials”
Kenji Katayama, Yaya Nagai, Zhenhua Pan

5/18, 10:10 Y1076, Poster
“コンボリューショナルニューラルネットワークを用いた SEM画像からの水分解光触媒電極性能の予測”
○林 祐太、永井 優也、潘 振華、片山 建二

3月20日(水) 9:00~ 11:40,  A1458-3am-01  
“Convolutional Neural Network Prediction of the photocurrent−voltage curve directly from scanning electron microscopic image for hematite ”
（畳み込みニューラルネットワークを用いた電子顕微鏡画像からの電流ー電圧曲線の予測-ヘマタイトを例に）
Shinichi Fujiwara, Yuta Hayashi, Yuya Nagai, Zhenhua Pan, Kenji Katayama

3月19日(火) 15:55 ~ 17:15,  A1458-2vn-03
“Prediction of photocurrent density of various photoanodes using machine learning with feature extraction from analytical data”
（分析データからの特徴抽出による機械学習を用いた種々の光アノードの光電流密度の予測）
Yuya Nagai, Zhenhua Pan, Kenji Katayama

3月20日(水) 13:00 ~ 15:30,  A1458-2pm-02
“Photosynthesis of hydrogen peroxide by a scalable reactor”
（大面積化に向けた反応器による過酸化水素の人工光合成）
Zhenhua Pan, Kenji Katayama, Shu Hu, Chiheng Chu

Nov 29, 11:20- 11:40 C033
"Observation of local charge carrier dynamics for Pt/TiO2 by using the time-resolved pattern-illumination phase microscopy"
Yuta Egawa, Zhenhua Pan, Kenji Katayama

Nov. 29, Poster, PP045
"Prediction of the photoelectrochemical performance of hematite electrodes using analytical data"
Yuya Nagai, Zhenhua Pan, Kenji Katayama