Abstract
The escalating concentration of atmospheric CO₂ poses a serious threat to global ecosystems and has profound impacts on climate change, necessitating urgent development of efficient and sustainable carbon conversion technologies. This doctoral thesis comprehensively explores the catalytic hydrogenation of CO₂ into value-added chemicals, with particular focus on methane (CH₄) production, through an innovative photothermal catalytic approach that synergistically utilizes solar energy and thermal energy. The research systematically investigates the design principles, synthesis methods, and mechanistic functions of transition metal-based catalysts, including nano zero-valent iron (NZVI), boron-doped nickel (B-Ni), and various bimetallic systems supported on Al₂O₃, employing a combined experimental and theoretical methodology.The investigation first establishes that NZVI catalysts can effectively drive the photothermal reduction of CO₂ when using H₂O as a sustainable hydrogen source, achieving remarkable conversion efficiency under mild reaction conditions. Through comprehensive experimental characterization and density functional theory (DFT) calculations, we reveal that the reaction proceeds through a sophisticated synergistic mechanism wherein H₂O dissociation provides essential active hydrogen species that significantly promote CO₂ activation and subsequent hydrogenation steps.
The study further demonstrates that boron doping represents an exceptionally powerful strategy for substantially enhancing the performance of Ni-based catalysts. Detailed DFT analysis confirms that subsurface boron incorporation effectively modulates the electronic structure of Ni surfaces, substantially weakening carbon monoxide (CO) adsorption strength and thereby successfully suppressing catalyst deactivation while dramatically boosting CH₄ selectivity to over 95%.
Further systematic investigation identifies the Ni-Al₂O₃ interface as an optimal and highly stable configuration among various catalyst structures, exhibiting superior CO₂ and CO adsorption properties compared to conventional extended Ni surfaces. The catalytic performance reaches its peak in carefully designed bimetallic systems, particularly in the B-Ni-Ru/Al₂O₃ configuration, which demonstrates exceptional CH₄ yield and remarkable long-term stability under continuous photothermal reaction conditions, primarily attributed to well-orchestrated synergistic metal-metal interactions and the effective promotional role of boron doping.
This research provides the intricate structure-activity relationships and detailed reaction mechanisms governing photothermal CO₂ hydrogenation over advanced transition metal catalysts. The significant findings highlight the crucial importance of metal-support interfaces, strategic dopant incorporation, and optimized bimetallic synergies in designing next-generation high-performance catalysts. By successfully bridging advanced material synthesis, in-depth spectroscopic characterization, and sophisticated theoretical modeling, this thesis makes substantial contributions to the development of efficient photothermal catalytic systems for CO₂ valorization, ultimately offering a promising and sustainable pathway for renewable fuel production and closing the carbon cycle through innovative catalytic technologies.
| Date of Award | 15 Jul 2026 |
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| Original language | English |
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| Supervisor | Tao Wu (Supervisor) & Xiang Luo (Supervisor) |