Liping Zhong

Compréhension à l'échelle atomique du fonctionnement des catalyseurs à base de CO pour l'oxydation préférentielle du CO en milieu riche en H2: Les performances d’un catalyseur sont connues pour être influencées par plusieurs facteurs, l’état d’oxydation de surface étant l'un des plus importants. Les catalyseurs à base de cobalt, qui apparaissent comme des matériaux prometteurs pour la réaction d'oxydation préférentielle du monoxyde de carbone dans un mélange riche en hydrogène (COPrOx), font cependant l'objet d'un débat intense ., au sujet de l'état d'oxydation de leurs sites actifs durant la réaction. Dans cette thèse, nous avons utilisé la technique de NAP-XPS en operando combinée avec d'autres méthodes de caractérisations in et ex situ pour corréler l'activité COPrOx à l'état d'oxydation du cobalt. Sur la base des résultats de NAP-XPS et NEXAF, CoO a été identifiée comme la phase optimale pour la COPrOx, tandis que les premiers calculs modélisation ont permis d’expliquer cettedécouverte. Il a également été noté que CoO est métastable et s'oxyde rapidement dans des conditions COPrOx conduisant à la désactivation du catalyseur.

The ratio (R) of the production rates of CH₃OH and CO from electrocatalytic CO₂ reduction on Co phthalocyanine is related to the average CO₂ mass-transfer rate (ν) by a power function (R = 0.97ν⁻0.78).

The catalyst-free CO₂ reduction with ammonia borane in the solid state is reported. Close to 40 mmol of CO₂ per gram of ammonia borane can be reduced at 0.5 MPa and 60 °C to formamide in high yield, achieving a highly atom-economical process.

A high content of acidic surface OFGs on a carbon support enables the fine dispersion of Co-based nanocatalysts, enhancing its OER mass activity, while also inducing additional COOH surface groups that act as O ₂ spillover sites.

A fluoropolymer bifunctional solid membrane interface (PTFE SMI) effectively inhibits anodic self-corrosion, while simultaneously reducing the accumulation of by-products, thereby facilitating the commercialization of aqueous Al–air batteries.

Methanation of CO₂ is an important reaction for reducing CO₂ emissions in a power-to-gas system. Compared to cobalt supported on gamma-Al₂O₃, cobalt supported on graphene nanoplatelets (GNPs) showed significantly better performance for CO₂ methanation. Cobalt supported on GNPs was capable of 15% conversion of CO₂ to CH₄ at temperatures below 250°C, compared to 5% for cobalt supported on Al₂O₃. In situ thermogravimetric analysis (TGA) demonstrated that the Co/GNP catalyst was stable to 400°C. The maximum catalyst mass-specific CH₄ yield was obtained at a Co loading of 5_wt% on GNPs; however, high Co loading on GNPs deactivated the reactivity of the Co/GNP catalyst. Transmission electron microscopy (TEM) demonstrated that 5_wt% Co/GNPs had the smallest and most dispersed cobalt nanoparticles. Excessive loading of cobalt tended to form isolated large Co nanoparticles. X-ray photoelectron spectroscopy (XPS) and Raman spectrometry revealed that more CoO phases were maintained on the surface of 5_wt% Co/GNPs, indicating that the interaction between the Co and the GNPs had more of an impact on cobalt’s redox capacity than did particle size, which ultimately affected cobalt’s active phase during the CO₂ reduction process. Furthermore, Raman spectrometry demonstrated that Co loading led to an increase in graphene defects. Higher Co loading on GNPs resulted in fewer interfaces between Co and GNPs due to the agglomeration of Co nanoparticles.

The atomically dispersed transition metal with nitrogen-doped carbon (M-N-C) has been studied as a possible replacement for platinum group metal (PGM) catalysts in fuel cell electrodes. In this work, the Fe-N-C and Co-N-C are used as a hydrogen peroxide reduction reaction (PRR) catalysts in direct borohydride fuel cells (DBFCs). Using half-cell and membrane electrode assembly (MEA) configurations, the PRR activity and durability of M-N-C are assessed. The Fe-N-C has higher activity on PRR than Co-N-C. Co-N-C is more stable than Fe-N-C under DBFC cathode, where hydrogen peroxide and sulfuric acid electrolyte are used as fuel. In the DBFC durability test, Fe-N-C demonstrates a performance loss of 18.6% following an accelerated durability test, whereas Co-N-C shows a more stable performance with a performance loss of only 6.7%. To examine the degradation mechanism of M-N-C, post-mortem XPS and Raman spectroscopy measurements are conducted. In addition, the density functional theory (DFT) simulation supports the Co-N-C stability on the catholyte. The usage of PGM catalysts is all replaced to transition metal catalysts in liquid fuel-operated DBFC systems.