Photo-thermal Synergistic Catalysis Of Methanol Reforming For Hydrogen Production Based On Semiconductor-supported Noble Metal Catalysts

With the increasingly serious environmental pollution problem and energy crisis,the development of clean energy carriers is the top priority of today’s development.Hydrogen energy is favored due to its high energy density,wide range of sources,and clean combustion products,and is expected to become a substitute for fossil energy.Methanol aqueous-phase reforming（APR）is one of the effective methods due to the good economy of methanol,high hydrogen content and low reforming reaction temperature.The traditional methanol APR reaction adopts two relatively independent catalytic systems,photocatalysis and thermal catalysis.Photocatalytic technology has mild reaction conditions and low energy consumption,but has poor response to long-wavelength light and low utilization of light energy;while thermocatalytic technology has relatively higher catalytic efficiency,but it also has the disadvantage of large energy consumption,which does not meet the Green environment concept.Photo-thermal synergistic catalysis is a new type of catalytic technology that integrates photocatalytic technology and thermal catalysis technology into the same catalytic system.It can catalyze reactions at lower temperatures and achieve higher catalytic efficiency.The advantages and disadvantages of technology and thermocatalytic technology complement each other.However,the current research on the photo-thermal synergistic catalysis of catalysts is not deep enough,and the mechanism research has not been thorough,which makes it difficult to modify the catalyst to improve the catalytic performance.In view of the above problems,the main research work of this thesis is as follows:1.Performance and mechanism of Pt/TiO₂ catalyst for photo-thermal catalysis of methanol APR for hydrogen productionBy in-situ photodeposition,Pt particles were deposited on the surface of Ti O₂,and then the catalyst was directly used in the catalytic reaction of methanol aqueous phase reforming for hydrogen production.The Pt/Ti O₂ catalyst exhibited efficient hydrogen evolution activity in the PC-TC reaction,which was 3 times that of the TC reaction and 7 times that of the PC reaction.Its physical characterization proved that the loading of Pt changed the structure and chemical environment of Ti O₂,thereby enhancing the catalytic performance of the catalyst.By studying its possible reaction mechanism,the results showed that the introduction of light in thermal catalysis enhanced the decomposition of water molecules,reduced the activation energy of the reaction,and effectively reduced the barrier of C-H bond cleavage,thereby improving the catalytic performance of the catalyst.2.Photo-thermal catalysis of methanol APR hydrogen production and mechanism of noble metal/photosensitive support catalystsThe PM/MO catalysts（PM=Pt,Pd;MO=P25,CeO₂,Zn O）were synthesized by in-situ photodeposition and directly used in the methanol APR catalytic system.The performance results showed that for the catalysts on the same semiconductor support,the difference of noble metals could significantly affect the performance of the catalysts,while for the catalysts loaded with the same active center on different semiconductor supports,the catalytic performance of the catalysts was significantly different due to the different interactions between them.difference.The physical characterization showed that after loading Pt on the three semiconductor supports,Pt had the greatest effect on the structural and chemical environment changes of P25,followed by Ce O₂,and the least change on Zn O,resulting in the ranking of the photoresponsive performance of the three catalysts as 0.1%Pt/P25>0.1%Pt/Ce O₂>0.1%Pt/Zn O,which was the direct reason for the difference in catalytic performance.The scavenger experiments showed that 0.1%Pt/P25 generated more hydroxyl radicals during the reaction process,which was beneficial to the water-gas shift experiment with the intermediate CO generated when the C-H bond of formaldehyde generated by methanol oxidation was broken,and the hydrogen yield was improved.