We have demonstrated that nanostructured conjugated polymers (NCPs) are highly active for water oxidation [Patel2020]. The electrons and protons produced from the photo-oxidation of water are stored on the nanostructured organic semiconductor. Thus, we successfully replicated the function of Photosystem II, a natural enzymatic complex in photosynthetic organisms (Figure 1). We are also developing multifunctional composite materials La_1-xTi_xFeO₃-NCP for water remediation. We have established a radiolytic method as an alternative to chemical and electrochemical methods for the synthesis in aqueous or organic media of various types of nanostructured conductive polymers or copolymers (CPs) [Bahry2018, Bahry2020, Bahry2021], which are functionally varied, with adjustable hydrophilicity and controlled morphology. We have shown that these CP nanostructures constitute a new class of photocatalysts, highly effective for environmental applications (degradation of organic pollutants) [Yuan2019,  Yuan2020a,Chouli2022], with visible light activity significantly exceeding that of most known photocatalysts. Composite nanomaterials based on CPs and clays or Covalent Organic Framework (COF) materials are also synthesized by radiolysis. This work has led to several international collaborations with teams from Poland, Japan, Mexico, Algeria, China, and India.

As part of a collaboration with Luxembourg and Belgium, "photonic" TiO₂ photocatalysts with modifiable 3D periodic architecture are synthesized through soft chemistry using cellulose as a structuring agent (Figure 2). These materials enhance the quantum yield and photocatalytic properties of TiO₂ without the need to add noble metals [Gesesse2019, CWang2020, CWang2021, CWang2023a]. We have developed heterojunctions based on the carbon allotrope "Graphdiyne" (Figure 3) for H₂ generation and CO₂ valorization. A simple synthesis method with a yield close to 100% has been established [Li2022]. The bandgap of these materials has been modified to render them photoactive for H2 production [Li2021,CWang2023b]. Regarding H₂ production, we have continued our work on the surface modification of TiO₂ or other semiconductors such as nanostructured conjugated polymers with bimetallic nanoparticles based on Ni, Fe, and plasmonic metals (Pd-Au, Ni-Au, Pt-Ni, etc.) induced by radiolysis and by porous materials of the Metal Organic Framework (MOF) type [Yuan2020b]. We have shown, for example, that nickel facilitates the formation of H-H bonds and that the hydrogen evolution rate is higher with co-modification with another metal, achieving a synergistic effect between the two metals [Wang2023]. Surface modifications of TiO₂ with copper-based MOFs have also yielded very promising results in terms of H₂ production [Martinez2019]. We are developing composite materials based on MOFs for H₂ generation and storage. The structure of these composite materials is crucial for photocatalytic applications. In collaboration with the Laboratory of Organic Polymer Chemistry and the Institute of Molecular Sciences, we have shown that a family of organic semiconductors based on conjugated donor-acceptor-donor trimers forms, under UV or visible irradiation, electron-hole pairs and is highly effective for H₂ production [Yuan2023]. Their remarkable photophysical, chemical, and electrical properties make them excellent candidates for solar energy conversion into chemical energy.

Core-shell photocatalysts are developed through soft chemistry for H₂ production and biomass valorization: metallic nanoparticles are encapsulated in a thin layer of TiO₂. The optimization of the interaction between the photocatalyst and the co-catalysts linked to the presence of defects at the nanoparticle/photocatalyst interface results in improved photophysical and photocatalytic properties [Gesesse2018, Gesesse2020, Ferraz2021].

Furthermore, perovskites prone to dissolution in aqueous media have also been stabilized by encapsulation in an inorganic matrix. Once stabilized, these materials demonstrated activity and stability during photocatalytic H₂ production [Knezevic2023].