Bulk Photodriven CO2 Conversion through TiO2@Si(HIPE) Monolithic Macrocellular Foams. (7th January 2019)

• Record Type: Journal Article
• Authors: Bernadet, Sophie; Tavernier, Eugénie; Ta, Duc‐Minh; Vallée, Renaud A. L.; Ravaine, Serge; Fécant, Antoine; Backov, Rénal
• Is Part Of: Advanced functional materials. Volume 29:Number 9(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-01-07
• Subjects: CO2 photoreduction -- heterogeneous catalysis -- integrative chemistry -- porous materials -- sol–gel process; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201807767
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: Operating photo‐induced reactions exclusively on catalyst surfaces while not exploiting the full catalyst volume generates a major footprint penalty for the photocatalytic reactor and leads to an inefficient use of the catalytic material. Photonic investigations clearly show that the solid foams have a strongly multidiffusive character, with photons being significantly trapped within the sample cores while addressing a photon mean free path l t = 20.1 ± 1.3 µm. This 3D process both greatly limits back‐reactions and promotes outstanding selectivity toward methane (around 80%) generation, and even ethane (around 18%) through C‐C coupling reaction, with residual carbon monoxide and dihydrogen contents (around 2%). Silica–titania TiO2 @Si(HIPE) self‐standing macrocellular catalysts lead to optimal efficient thicknesses up to 20 times those of powders, thereby enhancing the way for real 3D‐photodriven catalytic processes above the millimeter scale and up to a 6 mm thickness. A rather simple Langmuir–Hinshelwood based kinetic model is proposed which highlights the strong dependence of photocatalytic reaction rates on light scattering and the crucial role on oxidation back‐reactions. In addition, a strong correlation between light attenuation coefficient and photon mean free path and median pore aperture diameter is demonstrated, offering thus a tool for photocatalytic behavior prediction. Abstract : Novel TiO2 @Si(HIPE) monolithic macrocellular foams offer a path for real 3D photodriven CO2 conversion at the millimeter thickness length scale, a configuration where "thicker is better" appears as a new paradigm. The light trapping scenario and the associated photoinduced electron within the foams both limit back‐reactions and promote outstanding selectivity toward methane, as well as ethane generation through the C‐C coupling reaction.