Investigation of Heterogeneous Photocatalysts based on TiO2-Graphene Composites in Selective Synthetic Transformations

• Applicants: Professor Dr. Wolf Gero Schmidt; Professor Dr. René Wilhelm
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation ; Theoretical Chemistry: Molecules, Materials, Surfaces
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 413541925

• Final Report Year: 2023

Final Report Abstract

The development of catalysts that enable the utilization of light sources in the visible range (VIS), such as sunlight, holds significant interest for various applications. In this study, we prepared and characterized different composites of TiO2-GOx% hybrids. These composites were obtained by mixing either edge-functionalized graphene oxide or commercially obtained graphene oxide with various types of TiO2. Additionally, we investigated the influence of two different synthetic routes for these composites. The preparation process involved slowly evaporating the solvent after material mixing, followed by heat treatment (300-500°C) in a tube furnace or mechanical treatment with ultrasound to obtain the desired composites. Furthermore, we assessed the photocatalytic activity of the various nanocomposites by examining the adsorption and degradation of methyl orange (MO) and by exploring their photocatalytic performance in organic reactions. To gain deeper insights into the observed improved photocatalytic activity with light in the visible range with the graphene oxide/TiO2 hybrids, we employed density functional theory (DFT) calculations to identify potential contributing factors. Notably, we found that graphene oxide acts as a sensitizer rather than a co-catalyst, and a significant improvement in photocatalytic activity was observed only after thermal treatment. These findings offer valuable insights into the mechanisms and behavior of TiO2-GOx% hybrid composites, potentially leading to the development of more efficient and effective photocatalytic materials for diverse applications. We conducted first-principles total-energy and electronic-structure calculations based on densityfunctional theory to explore the structure and catalytic properties of model systems selected corresponding to the synthesized material. To address the excited states relevant for photocatalysis, we utilized calculations beyond ground-state DFT, including constrained DFT, time-dependent DFT, and many-body perturbation theory. Our calculations revealed that GO can function as an electron reservoir, not just an electron sink, when combined with TiO2 and other photocatalysts.

Publications

• Water Splitting Reaction at Polar Lithium Niobate Surfaces. ACS Omega, 4(2), 3850-3859.
  Dues, Christof; Schmidt, Wolf Gero & Sanna, Simone
  
• A photoredox catalysed Heck reactionviahole transfer from a Ru(ii)-bis(terpyridine) complex to graphene oxide. RSC Advances, 10(70), 42930-42937.
  Rosenthal, Marta; Lindner, Jörg K. N.; Gerstmann, Uwe; Meier, Armin; Schmidt, W. Gero & Wilhelm, René
  
• Photocatalytic properties of graphene‐supported titania clusters from density‐functional theory. Journal of Computational Chemistry, 41(21), 1921-1930.
  Badalov, Sabuhi V.; Wilhelm, René & Schmidt, Wolf G.
  
• Photochemical Ring Opening of Oxirane Modeled by Constrained Density Functional Theory. ACS Omega, 5(37), 24057-24063.
  Krenz, Marvin; Gerstmann, Uwe & Schmidt, Wolf Gero
  
• Adatom mediated adsorption of N‐heterocyclic carbenes on Cu(111) and Au(111). Journal of Computational Chemistry, 43(6), 413-420.
  Jain, Mitisha; Gerstmann, Uwe; Schmidt, Wolf Gero & Aldahhak, Hazem
  
• Controlled growth of ordered monolayers of N-heterocyclic carbenes on silicon. Nature Chemistry, 13(9), 828-835.
  Franz, Martin; Chandola, Sandhya; Koy, Maximilian; Zielinski, Robert; Aldahhak, Hazem; Das, Mowpriya; Freitag, Matthias; Gerstmann, Uwe; Liebig, Denise; Hoffmann, Adrian Karl; Rosin, Maximilian; Schmidt, Wolf Gero; Hogan, Conor; Glorius, Frank; Esser, Norbert & Dähne, Mario
  
• Diquat Based Dyes: A New Class of Photoredox Catalysts and Their Use in Aerobic Thiocyanation. Chemistry – A European Journal, 29(22).
  Meier, Armin; Badalov, Sabuhi V.; Biktagirov, Timur; Schmidt, Wolf Gero & Wilhelm, René
  
• Rutile, anatase, brookite and titania thin film from Hubbard corrected and hybrid DFT. Materials Research Express, 10(7), 075501.
  Badalov, S. V.; Bocchini, A.; Wilhelm, R.; Kozub, A. L.; Gerstmann, U. & Schmidt, W. G.
  
• Synthesis of new graphene oxide/TiO2 and TiO2/SiO2 nanocomposites and their evaluation as photocatalysts. Catalysis Science & Technology, 13(15), 4367-4377.
  Rosenthal, Marta; Biktagirov, Timur; Schmidt, Wolf Gero & Wilhelm, René