Patrick Mountapmbeme Kouotou

Selective synthesis of α-Fe2O3 thin films and effect of the deposition temperature and lattice oxygen on the catalytic combustion of propene

Pulsed spray evaporation chemical vapour deposition (PSE-CVD), an elaborate CVD process, was employed to synthesize thin films of α-Fe2O3 for the catalytic combustion of propene. According to X-ray diffraction and Raman spectroscopy, the alpha structure type was presented as the unique phase. α-Fe2O3 with fine crystalline structure was revealed by scanning electron microscopy, and probed in depth for the first time by helium ion microscopy. Energy dispersive X-ray microscopy and X-ray photoelectron spectroscopy displayed an overview of the chemical composition of the samples. In situ emission FTIR spectroscopy was used for the accurate determination of the thermal stability of the samples at around 500 °C, and temperature-programmed reduction was performed to correlate the catalytic performance and reduction properties of the obtained α-Fe2O3 thin films. The results showed that the increase of the deposition temperature leads to significant changes of film morphology, chemical composition and reduction properties, with a direct consequence on the catalytic performance. α-Fe2O3 prepared at a low temperature (350 °C) exhibited high activity towards the deep oxidation of propene, which was attributed to its good reducibility and the plate-like structures. The alternate reduction and oxidation of the oxide surface (favored by the bulk oxygen migration towards the surface) and replenishment of bulk oxygen by gas-phase oxygen suggest that the oxidation of propene may proceed according to the Mars van Krevelen mechanism. The morphology and surface composition of the prepared samples remain the same before and after the catalytic test, demonstrating very good stability and reproducibility. We thus conclude that α-Fe2O3 effective in propene conversion can be selectively synthesized with PSE-CVD.

Controlled synthesis of Co3O4 spinel with Co(acac)3 as precursor

Cobalt(III) acetylacetonate (Co(acac)3) was used as a precursor to grow pure Co3O4 with pulsed-spray evaporation chemical vapor deposition (PSE-CVD). The effect of solvent and substrate temperature on the growth kinetics and morphology of the films was investigated. The obtained spinel exhibited good catalytic performance.

Facile synthesis of efficient Cu-Co-Fe ternary oxides by pulsed-spray evaporation PSE-CVD for CO oxidation

-1 -1 hourly space velocity (GHSV) of 75,000 mL g h . The results disclosed the formation of amorphous structure of ternary oxides with dome-top-shaped morphology which supplied abundant sites for oxygen evolution. The optical bandgap energies (1.5 and 2.05 eV) of asprepared ternary oxides were lower than their base metal oxide counterparts (2.15-2.18 eV), which enhanced their reducibility due to easier lattice oxygen mobility. The Cu-Co-Fe ternary oxides revealed excellent performance for CO oxidation. The superior performance was

CVD‐Made Spinels: Synthesis, Characterization and Applications for Clean Energy

To reduce emissions and protect environment from pollution caused by volatile organic compounds (VOCs) and CO, catalytic oxidation can be applied as an efficient and promising technique. This review provides a novel and facile strategy to synthesize spinel-type and non-spinel-type transition metal oxides (TMOs). Specifically, single (Co3O4, α-Fe2O3, Mn3O4, CuO, Cu2O and Cr2O3) and binary (Co3-xCuxO4, Co3-xMnxO4 and Co3-xFexO4) TMOs have been prepared using pulsed spray evaporation chemical vapor deposition approach (PSE-CVD). PSE-CVD offers several advantages over conventional methods, such as relatively low cost, simplicity and high throughput, which makes it a promising strategy. Moreover, the PSE delivery system allows using less stable precursors and permits improving the reproducibility of the film properties with tailored compositions. The above listed TMOs prepared by PSE-CVD were successfully tested as catalysts toward the complete oxidation of some real fuels such as CO, C2H2, C3H6, n-C4H8 and C2H6O as representatives of VOCs and industrial exhaust streams. The active TMOs explored in this review could be potential catalysts candidates in one of the research areas that are currently under scrutiny, as the battle for the future of energy and environment involves the generation and application of clean energy.