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Photocatalytic reduction of carbon dioxide in presence of mesoporous TiO2 photocatalysts

Reli Martin,1 Nadrah Peter,2 Filip Edelmannová Miroslava,1 Ricka Rudolf,1 Sever Škapin Andrijana,2, 3 Lavrenčič Štangar Urška,4 Kočí Kamila1*


1VŠB-TUO, CEET, Institute of Environmental Technology, 17. listopadu 2172/15, 708 00, Ostrava-Poruba, Czech Republic

2Slovenian National Building and Civil Engineering Institute, Ljubljana, Slovenia.

3Faculty of Polymer Technology - FTPO, Ozare 19, 2380 Slovenj Gradec, Slovenia

4University of Ljubljana, Faculty of Chemistry and Chemical Technology, Večna pot 113, 1000 Ljubljana, Slovenia.



In this study, we systematically explored the influence of different synthesis procedures (template-free and template-based routes using two copolymers of poly(ethylene oxide) and poly(propylene oxide)) on the carbon dioxide photocatalytic reduction activity of mesoporous TiO2. Our primary focus was to identify key factors affecting the photocatalyst's efficiency and selectivity. To establish meaningful comparison, we also evaluated the commercial photocatalyst P25 alongside the newly synthesized TiO2 photocatalysts. Among the investigated materials, the pure anatase form of TiO2, designated as TiO2-P123, exhibited the highest photoreduction efficiency and selectivity for carbon dioxide photocatalytic reduction. In contrast, the photocatalysts TiO2-EG, TiO2-F127, and P25, which consisted of a combination of rutile and anatase, demonstrated decreased photoactivity due to two factors. Firstly, the formation of a type II heterojunction between anatase and rutile resulted in reduced reducing power. Secondly, rutile's higher affinity for oxygen adsorption on its surface led to subsequent reduction to superoxide ions, further diminishing the photoactivity of these multiphase photocatalysts.

Moreover, we found that the chemicals used for the photocatalyst preparation significantly impacted the specific surface area. As expected, the most active photocatalyst, TiO2-P123, exhibited the highest specific surface area among the tested photocatalysts. Higher specific surface areas provided more reactive sites, thereby improving light absorption efficiency and extending the lifetime of photogenerated electron-hole pairs, resulting in enhanced photocatalytic activity. Apparent quantum yields were also calculated confirming our claims.



The work was supported by Large Research Infrastructure ENREGAT (project No.LM2023056), GA CR 21-24268K. The authors also thank the financial support provided by the Slovenian Research Agency (Grant Nos. N2-0188, P2-0273 and P1-0134).