Controllable Synthesis Of Hetrrojunction Catalytic Nanomaterials And Their Electrocatalytic Performance

Heterojunction nanomaterials have been widely applied in various types of catalytic reactions due to their unique physical and chemical properties. In recent years, the ever-increasing energy problems have stimulated intense attention on the research of fuel cells. Pt-based catalysts are the main catalysts in direct methanol fuel cells (DMFCs) currently. However, a number of obstacles associated with the loading of Pt, including high price, insufficient activity and durability, and ready poisoning by intermediates, still hinder their commercial application of DMFCs. Developing direct methods for preparation of Pt-based catalyst with low content of platinum and synthesis of other catalysts to replace Pt-based catalyst are urgent topic to be solved.Based on this research background, we systematically studied the synthesis of heterojunction nanomaterials and their electrocatalytic performance toward methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). The main contents in this thesis include following aspects:(1) A series of well-dispersed bimetallic Pd@Pt nanodendrites uniformly supported on XC-72 carbon black were fabricated by using different surfactant. These Pd@Pt/C catalysts were used as the anode catalyst for direct methanol fuel cells. In this thesis, we remove the surfactant through a facile reflux procedure, then the catalysis performance of the Pd@Pt/C catalysts enhanced obviously. The results indicates that, after treated with hot water, the Pd@Pt/C catalysts which prepared in the presence of P123 had greatest ECS A and showed excellent catalytic performance.(2) As a catalyst for methanol electro-oxidation and the hydrogenation reaction of 4-nitrophenol (4-NP), a novel dual-heterostructural nanocatalyst (Fe3O4@CeO2/M (M=Pt, Pd, Pt-Pd)) was fabricated. These dual-heterostructural features, which favor reactant diffusion and active sites exposure, and the synergistic catalytic effects among each component can dramatically enhance catalysis performance. The results indicate that the Fe3O4@CeO2/Pt (20 wt%) catalyst exhibits superior electrochemical activity towards the methanol oxidation in alkaline solution, and the Fe3O4@CeO2/Pd (3wt%) catalyst exhibits superior catalytic activity in the hydrogenation reaction of 4-nitrophenol (4-NP).(3) Ni-rGO-precursors with heterojunction structure were synthesized by a solvothermal method. By changing the calcination temperature and the content of graphene, the Ni3N/N-rGO composites nanomaterials, which were used as a catalyst for the oxygen reduction reaction were obtained. The results indicated that the Ni3N/N-rGO (30 wt%) composite nanomaterial calcined at 380℃ exhibits superior catalytic performance towards ORR. The half-wave potential values for Ni3N/N-rGO (30 wt%)is 0.76 V vs RHE.