Synthesis Of Cluster-Based Crystalline Chalcogenide Materials Containing Maganese Ions And Their Oxygen Reduction Catalytic Property

Energy shortage and environmental pollution increasingly become serious due to the rapid economic development and population growth.Fuel cells and metal-air batteries with the advantages of high specific energy,non-toxicity,and low pollution could bring new ideas to solve the aforementioned problems.In such batteries,the catalyst-assisted cathode surface oxygen reduction reaction(ORR)plays a crucial role.ORR research on the electrode surface has become a hot topic in the field of electrocatalysis.Although Pt-based noble metals exhibit extremely high electrocatalytic activity,it is of great significance to develop the non-noble ORR catalysts for fuel cell due to the high price and poor stability of noble catalysts.Manganese sulfides are one of importance electrocatalysts duo to low cost,high abundance,non-pollution and high catalytic activity.However,the manganese sulfide electrocatalysts previsouly reported have the disadvantages of large size,difficulty in dispersion and understanding of catalytic mechanism,leading to the slow research progress.At present,cluster-based metal chalcogenide crystalline materials with precise structure have potential to solve the aforementioned problems:introducing active metal manganese by doping,dispersed into homogeneous nanoclusters by ultrasonication,and the accurate atomic distribution and structure contributing to study the catalytic mechanism.Thus,the synthesis and electrocatalysis of cluster-based crystalline chalcogenide materials containing manganese ions are well worth to study.In this thesis,the stable metal chalcogenide materials containing Mn ion were synthesized via solvothermal method by in-situ synthesis and/or postreatment.The synthesis conditions and thermal stability were discussed,and the oxygen reduction catalytic properties were further studied especially.The main works are summarized as follows:1.Monodisperse ultrasmall manganese-doped multimetallic oxysulfide nanoparticles as highly efficient oxygen reduction electrocatalystThe stable P1 isolated clusters were prepared by solvothermal method,and the in-situ manganese-doped ones(P1-Mn)were also created.A uniformly dispersed Mn-doped P1-Mn NPs with diameter 3.5 nm was obtained while the P1-Mn precursor was ultrasonicated in water-ethanol system.Under 1 M KOH condition,P1-Mn NPs show better catalytic performance,stability and methanol resistance than commercial Pt/C(20 wt%)which should be attributed to Mn(III)species on the particle surface.This study not only offers a new method for the synthesis of non-noble metal catalysts,but also provides the possibility and theoretical basis for the potential applications in energy conversion and storage of the isolated metal chalcogenide nanoclusters,and provides the research new idea for structure-activity relationship.2.Chalcogenide framework built from supertetrahedral T3 cluster and metal momplex and its ORR propertyA neutral crystalline framework material(NCF-4)with typical diamond topology was obtained via solvothermal method.It is constructed by supertetrahedral T3 cluster([Mn2Ga4Sn4S20])as building unit and metal complex([Mn(dach)2](dach=1,2 diamino-cyclohexanes)as linker.ORR performance of NCF-4 was evaluated in 0.1 M KOH solution at room temperature.NCF-4 exhibits high-efficiency electrocatalytic oxygen reduction activity,better than that of commercial Pt/C(10 wt%).NCF-4 has strong coordination bonds,and it is difficult to disperse into nanoclusters or small-sized nanoparticles,which cause that catalytic performance of NCF-4 is lower than that of P1-Mn NPs.This work provides the further theoretical guidance for cluster-based crystalline chalcogenide materials containing manganese ions as ORR catalysts.3.Synthesis of 1-D copper selenides and their near-IR photoelectric responseTwo isostructural 1-D copper selenides were obtained by solvothermally method.They are constructed by anionic chains of[Cu2MSe5]4-(M=Ge,Sn)with the existence of strong Cu…Cu interaction in it and complexes of[mn(H+-en)2(en)].Their copper-induced narrow-band gap makes them exhibiting NIR-triggered photoelectric response.The project not only better expands the types of clusters-based chalcogenide crystalline materials containing Mn2+ ions,but also provides the basic theoretical guidance for their feasibility as ORR catalysts.