Photocatalysts take the lead in global battle against microplastic pollution

Amidst the rising concerns over the environmental and health risks posed by microplastic and nanoplastic pollution, a new bibliometric study reveals an unprecedented rise in scientific efforts targeting photocatalytic degradation of these persistent pollutants. The findings signal a growing momentum toward developing sustainable and efficient solutions for plastic waste treatment using light-driven nanomaterials.

The study, titled “Global Research Trends in Photocatalytic Degradation of Microplastics: A Bibliometric Perspective”, was published in Microplastics by Robert O. Gembo, Zebron Phiri, Lawrence M. Madikizela, Ilunga Kamika, Lueta-Ann de Kock, and Titus A. M. Msagati. It provides a comprehensive analysis of 204 peer-reviewed articles published between 2005 and October 2024, using data from the Web of Science and Scopus databases. Through the use of bibliometric software tools such as Bibliometrix, Biblioshiny, and VOSviewer, the research tracks academic productivity, leading countries and institutions, frequently used photocatalysts, and collaborative networks in this growing scientific domain.

How has research on photocatalytic microplastic degradation evolved globally?

The analysis reveals a significant acceleration in research output over the past two decades, with a compounded annual growth rate of 17.94%. The number of studies focusing on photocatalytic degradation of microplastics and nanoplastics has surged particularly since 2019, correlating with increased global awareness and policy discourse on plastic pollution in aquatic systems.

China emerges as the dominant contributor, accounting for 41.7% of all publications. This is followed by India, Mexico, the United Kingdom, and Japan. China’s role is not only quantitative but also influential, with its research forming the backbone of numerous international collaborations. Notably, Italy, Iran, and Saudi Arabia have demonstrated high levels of multi-country cooperative output, often engaging with partners in China, the United States, and South Korea.

Key research institutions identified include the Universidad Autónoma de Nuevo León in Mexico and the University of Calcutta in India. These institutions are recognized for their significant publication volumes and their role in shaping the academic discourse on photocatalytic methods for degrading plastic micropollutants.

The authors of the study underscore that the rapid expansion in this field reflects not only a response to environmental urgency but also a diversification of technological approaches and geographic participation. The spread of publications across continents indicates an increasingly global scientific consensus on the need for photodegradation technologies to combat microplastic accumulation.

What are the most frequently studied materials and mechanisms?

The study categorizes the primary materials and strategies used in photocatalytic degradation research. Titanium dioxide (TiO₂) leads as the most extensively studied photocatalyst, prized for its high photocatalytic activity, chemical stability, and availability. However, other materials such as zinc oxide (ZnO), graphitic carbon nitride (g-C₃N₄), and various doped semiconductors are gaining traction due to their enhanced light absorption and reactivity.

Common target polymers include polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), which reflect the dominant microplastics found in marine and freshwater systems. These polymers are often used in experimental setups to simulate real-world degradation conditions.

Photocatalytic degradation functions through the excitation of semiconductor materials under light irradiation, leading to the generation of reactive oxygen species that break down plastic polymers. The process is considered eco-friendly as it requires no harmful chemicals and operates under ambient conditions when sunlight or simulated light is available.

The reviewed studies also highlight innovations in material modification aimed at improving degradation efficiency. Techniques include the formation of heterojunctions, doping with metal or non-metal elements, and the integration of photocatalysts into membrane or composite systems. These innovations enhance charge separation, broaden light absorption spectra, and improve interaction with plastic particles.

Beyond material performance, researchers are increasingly focusing on understanding degradation byproducts, mineralization efficiency, and the environmental safety of residual nanomaterials. These secondary concerns are crucial for validating photocatalysis as a viable treatment method for real-world implementation.

What trends, collaborations, and future directions are emerging?

The bibliometric mapping uncovers significant collaborative activity and shifting thematic emphases. While early studies were more experimental and confined to laboratory-scale assessments, recent research shows a trend toward multidisciplinary integration involving environmental science, nanotechnology, materials engineering, and toxicology.

Keyword clustering and co-occurrence analyses suggest growing interest in green chemistry approaches, sunlight-driven processes, and environmental fate assessment of degradation products. There is also an increasing tendency to pair photocatalysis with hybrid systems such as advanced oxidation processes, which offer complementary mechanisms for more complete plastic breakdown.

Funding patterns and authorship networks also point to intensified collaboration among Asian and Middle Eastern countries, with China acting as a central node. The evolution of research topics over time, from initial studies on material synthesis to current concerns around circular economy implications, demonstrates the field’s maturation and alignment with broader sustainability goals.

The authors emphasize the need for future research to address scalability, cost-effectiveness, and lifecycle assessments. For photocatalytic technologies to move beyond the laboratory, questions of real-world deployment, such as catalyst durability, water matrix effects, and maintenance requirements, must be systematically resolved.

The review calls for enhanced North–South and South–South collaborations, knowledge transfer mechanisms, and policy engagement to ensure that emerging photocatalytic solutions are equitably developed and deployed in regions most impacted by plastic pollution.