Immobilization of Co, Mn, Ni and Fe oxide co-catalysts on TiO for photocatalytic water splitting reactions

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2019-08, Vol.7 (31), p.18568-18579
• Main Authors: Schubert, Jasmin S, Popovic, Janko, Haselmann, Greta M, Nandan, Sreejith P, Wang, Jia, Giesriegl, Ariane, Cherevan, Alexey S, Eder, Dominik
• Format: Article
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c9ta05637h

Here we report a systematic study of a series of non-noble-metal co-catalysts based on Co, Mn, Ni and Fe oxides that were prepared by wet impregnation of the corresponding acetylacetonate precursors onto a model TiO 2 substrate, followed by their oxidative decomposition. We analyze thermal evolution of the impregnated M(acac) x TiO 2 composites with a combination of analytical methods and reveal strong differences in the precursor decomposition onsets and the resulting product composition, compared to the case of pure M(acac) x precursors. Consequent electron microscopy analyses of the resulting MO x TiO 2 composites indicate the presence of small (15 nm) amorphous MO x nanoparticles that are homogeneously distributed on the surface of the substrate TiO 2 . Complementing Raman and photoluminescence (PL) spectra confirm pronounced effects of MO x deposition on the state of TiO 2 substrate and suggest strong electronic communication between the components. The composites obtained at 350 C were further tested towards sacrificial hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) demonstrating the dynamic nature of the NiO x TiO 2 photocatalyst whose Ni 0 active HER sites were generated in situ upon light exposure. In contrast, FeO x TiO 2 , CoO x TiO 2 , and NiO x TiO 2 were all active towards OER, featuring water oxidation ability in descending order, while XPS data of the samples after reaction indicate that partial oxidation of M species takes place during the course of the photocatalytic experiment. This work provides detailed insights on the wet chemistry-based preparation of MO x co-catalysts decorating oxide nanopowders including optimization of the thermal treatment, potential substrate effects and synergy as well as further prospects in photocatalysis. Here we report a systematic study of Co, Mn, Ni and Fe oxides as co-catalysts for HER and OER that were prepared by wet impregnation of the corresponding metal acetylacetonate salts onto a model TiO 2 substrate.