Design Of Non-noble-metal Catalysts For Photothermal Carbon Dioxide Hydrogenation

The use of sunlight and photothermal catalytic materials to convert carbon dioxide and hydrogen produced from renewable energy into high value-added fuels is expected to realize the efficient conversion of solar energy to chemical energy.Most of the existing photothermal catalysts use precious metal catalysts such as Ru and Pd with strong H2 and CO2 activation capabilities,but their large-scale application is limited by low reserves and high costs.Therefore,high-efficiency non-noble metal photothermal catalysts with low design costs and abundant reserves are receiving more and more attention.Although researchers have developed a variety of non-precious metal photothermal catalysts,their photothermal conversion capacity,intrinsic thermal catalytic performance,and stability are still passable for practical applications.Aiming at the shortcomings of the existing system,this thesis starts from the aspects of light absorption,thermal management and intrinsic thermocatalytic performance,and develops new strategies to improve the activity,selectivity and stability of non-noble metal-based photothermal catalysts.The specific research content is as follows:In the second chapter,a Ni@SiO2 core-shell structure photothermal catalyst is designed.The "nano-greenhouse effect" of the SiO2 shell reduces the heat dissipation of Ni nanoparticles and greatly improves the photothermal conversion efficiency and photothermal catalytic performance of the catalyst.Under 2.8 W/cm2 illumination,the carbon dioxide conversion rate reached a record-breaking 20.6 mol·gNi-1·h-1,which is nearly an order of magnitude higher than that of traditional catalysts.In addition,the confinement protection effect of silica also enhances the anti-sintering and carbon deposition ability of Ni nanoparticles.Under long-term working conditions,the core-shell structure photothermal catalyst exhibits good stability.This research reveals the importance of micro thermal management for the performance of photothermal catalysts,and provides new ideas for constructing efficient photothermal catalytic systems.On the basis of the work in the previous chapter,the third chapter of this paper further explored the influence of different substrates on the photothermal catalytic performance of commercial Ni catalysts from the perspective of macro thermal management.Studies have found that the use of a glass substrate with poor thermal conductivity can reduce the heat dissipation of the catalyst,thereby increasing its working temperature under light conditions,and ultimately leading to the improvement of photothermal catalytic performance.This study reveals that the heat conduction and heat dissipation between the catalyst and the substrate is a key factor affecting the photothermal performance of the catalyst,which provides a certain theoretical guidance for the design of the photothermal catalytic reactor.In addition to optimizing thermal management,reducing the size of non-precious metal nanoparticles is expected to improve its intrinsic thermal catalytic performance,but small-sized nano-particle photothermal catalysts still have the bottleneck problems of low photothermal conversion efficiency and poor stability.In Chapter 4,a cobalt-based photothermal catalyst combining plasmon hybridization effect,nano-greenhouse effect and spatial confinement effect is designed.Specifically,by encapsulating tightly packed small-sized Co nanoparticles in a silica nanorod array,the light-to-heat conversion efficiency and thermal stability were effectively improved.Under the light condition of 2.5 W/cm2,the activity of the catalyst reached 2.2 mol·gCo-1·h-1,the selectivity of CH4 was close to 100%,and it showed better stability.This study reveals the great potential of small-sized nanoparticles in photothermal catalysis,and provides a new way to construct high-efficiency non-noble metal photothermal catalysis.