Kindai University Assoc. Prof. Tetsuro Soejima's Photocatalytic H2O2 Synthesis Research Selected as Pivotal Paper in Photochemistry

Kindai University’s Photocatalytic Breakthrough Gains Global Recognition

Kindai University, a leading private institution in Japan renowned for its contributions to science and engineering, has once again demonstrated its prowess in cutting-edge research. Associate Professor Tetsuro Soejima from the Department of Applied Chemistry, Faculty of Science and Engineering, has had his groundbreaking work on photocatalytic hydrogen peroxide (H₂O₂) synthesis selected as a pivotal paper in the field of photochemistry by the Royal Society of Chemistry (RSC). This recognition, part of the "Most popular articles 2025: photochemistry collection" in Chemical Science, underscores the transformative potential of his innovations for sustainable chemical production.

Hydrogen peroxide, a versatile chemical used in everything from wastewater treatment to advanced electronics manufacturing, traditionally relies on energy-intensive processes involving hydrogen gas and anthraquinone. Soejima’s approach leverages sunlight, water, and oxygen—abundant and renewable resources—to produce H₂O₂ efficiently, aligning with Japan’s national goals for carbon neutrality by 2050.

The Science Behind the 500% Quantum Yield Achievement

In their seminal 2025 paper published in Chemical Science, Soejima and collaborators developed a nanocomposite photocatalyst composed of antimony-doped tin oxide (ATO) and zinc oxide (ZnO) nanoparticles. This material, prepared through a simple mixing, drying, and calcination process using commercially available precursors, exhibits extraordinary performance.

The process begins with photoexcitation under visible light, where ZnO generates electron-hole pairs. Electrons reduce oxygen to form superoxide radicals, which convert to H₂O₂ via a two-electron oxygen reduction reaction (ORR). Meanwhile, holes oxidize ethanol (added as a sacrificial agent) to produce hydroxyl radicals that initiate a chain reaction, amplifying H₂O₂ production. This synergy results in an external quantum yield (EQY) of approximately 500%—meaning five H₂O₂ molecules per incident photon—and a concentration of 162 mmol/L, over three times the prior record.

• Photoexcitation of ZnO generates charge carriers.
• Electrons drive ORR; holes trigger radical chain from ethanol oxidation.
• Radical propagation yields faradaic efficiencies >200% on the oxidation side.

This exceeds the conventional 100% limit by coupling photocatalysis with non-photochemical radical propagation, a paradigm shift explained through photoelectrochemical measurements and isotopic labeling.

Tetsuro Soejima: From Kyushu to Kindai’s Photocatalysis Pioneer

Assoc. Prof. Soejima’s career trajectory exemplifies dedication to nanomaterial innovation. Earning his Ph.D. from Kyushu University in 2007, he conducted postdoctoral research at UC Berkeley and back at Kyushu before joining Kindai University in 2010. Promoted to Associate Professor in 2022, his work spans colloid chemistry, self-organization, and photocatalysts.

Prior achievements include awards like the Gold Poster Award from the Japan Research Institute of Material Technology (2015) and Outstanding Reviewer for RSC Advances (2021). His focus on H₂O₂/H₂O₂-PCP (simultaneous reduction-oxidation photocatalysis) has produced follow-up reviews in Chemical Communications and Chemistry – A European Journal, cementing his leadership.

"The selection is a great honor," Soejima stated. "Clean photocatalytic H₂O₂ synthesis will lead photochemistry as H₂O₂’s importance grows."

Kindai University’s Legacy in Photocatalysis Research

Kindai University (formerly Kinki) has positioned itself as a hub for photocatalysis, with faculty like Prof. Hiroshi Kominami pioneering "solar chemical factories." The Department of Applied Chemistry emphasizes practical nanomaterial synthesis for energy and environmental applications, supported by state-of-the-art facilities.

This ecosystem fosters collaborations, as seen in Soejima’s work with Nagoya University’s Hiroaki Tada. Kindai’s emphasis on translational research aligns with Japan’s Society 5.0 vision, producing graduates ready for industry R&D roles in semiconductors and green chemicals.

Global and Japanese Context of Photocatalytic H₂O₂ Advances

Photocatalytic H₂O₂ addresses the limitations of the anthraquinone process, which consumes 1.5% of global hydrogen production. Globally, quantum yields near 100% via ORR-only systems exist, but Soejima’s >100% via dual pathways sets new benchmarks.

In Japan, where H₂O₂ production hit ~400 thousand tonnes in 2023 (projected CAGR 3.9% to 2033), green alternatives support the hydrogen society initiative. Universities like Tokyo Tech and Hokkaido contribute, but Kindai’s simple, scalable catalyst stands out.

Read the original Chemical Science paper for mechanistic insights.

Practical Applications: From Chemicals to Fuel Cells

H₂O₂ serves as a bleaching agent (pulp/paper), disinfectant, semiconductor cleaner, and propellant. In fuel cells, direct H₂O₂ cells offer high energy density without platinum catalysts or hydrogen storage issues.

Japan’s electronics sector (e.g., ultrapure H₂O₂) demands sustainable supply; photocatalytic on-site production reduces transport emissions. Pilot studies envision solar-powered units for remote manufacturing.

• Wastewater treatment: Advanced oxidation processes (AOPs).
• Electronics: Wafer cleaning without halides.
• Fuel cells: 1.5V vs. 0.7V for H₂/O₂.

Economic and Environmental Impacts in Japan

Japan’s H₂O₂ market, valued at ~USD 229M in 2025, grows with electronics and water treatment. Green production cuts energy use by 90% vs. conventional, supporting net-zero goals. Kindai’s IP could spawn startups, creating jobs in Osaka’s tech corridor.

Challenges include scaling to industrial rates (current lab: mmol/L/hr; need mol/L/hr) and stability under sunlight.

Future Directions and Challenges Ahead

Soejima’s reviews outline H₂O₂/H₂O₂-PCP optimization: bandgap tuning, co-catalysts, reaction media. Prospects include pure water systems and tandem fuel cells.

Collaborations with industry (e.g., Mitsubishi Gas Chemical) could accelerate commercialization. For Japanese higher ed, this highlights private universities’ role in applied research amid declining births and funding pressures.

Implications for Japanese Higher Education and Research Careers

Kindai’s success attracts talent to photocatalysis programs, with opportunities in JSPS fellowships and industry partnerships. For aspiring researchers, Soejima’s path—PhD, postdocs abroad, tenure-track—offers a model.

This positions Kindai among Japan’s top research unis for materials science, fostering interdisciplinary ties with engineering and environmental studies.

Photo by Bhupathi Srinu on Unsplash

Stakeholder Perspectives and Broader Recognition

RSC’s selection, based on citations/downloads/altmetrics, reflects global impact. Japanese media hailed it as "leading photochemistry." Peers praise the accessible synthesis, enabling replication worldwide.

Industry stakeholders see pathways to decarbonized chemicals; policymakers align with METI’s green innovation funds.