Preparation And Performance Study Of Manganese-based Electrocatalytic Materials For Oxygen Reduction And Hydrogen Evolution Reactions

Developing renewable energy and related technology is the only way to alleviate the greenhouse effect and achieve high-quality economic development.New-type energy devices such as fuel cell,metal air batteries and hydrogen production technology by water electrolysis which possess the advantages of cleanness,high efficiency and environmental friendliness have attracted extensive attention in recent years.In addition,electrocatalyst is the main factor that concerned with energy storage and conversion efficiency of these devices.Oxygen evolution reaction（OER）,hydrogen evolution reaction（HER）and oxygen reduction reaction（ORR）are significant electrode reactions in the above technologies.Designing and synthesizing corresponding electrocatalysts to replace the current commercial Pt/C,RuO₂ or IrO₂ noble metal catalysts for the reduction of energy barrier and improvement of reaction rate is an important part to realize the practical application of electrocatalytic energy technology.However,these precious metals which are low in reserve and high in price seriously restrict their large-scale application.In contrast,manganese based catalysts hold great expectaion to become substitute of the above benchmark catalysts for their rich reserves,low price,low toxicity,and excellent reactivity.In this thesis,the main contents are as follows:（1）Reducing the size of noble metals and combining with transition metal oxides has been proved to be one of the most effective means to improve the performance of Ir-based oxygen evolution catalyst.In view of this,we report a simple method to uniformly disperse ultra-small Ir clusters onto MnO₂ nanorods for OER in full pH range.In a series x%-Ir-MnO₂ samples（x refers to the mass percentage of Ir）,the OER performance of 5%-Ir-MnO₂ is better than that of other samples and also exceeds IrO₂.Under different media,to reach a current density of 10m A cm^-2,it requires overpotentials of 330 mV（0.2 M PBS,pH=7.0）,240 mV（1 M KOH,pH=14.0）and 267 mV（0.5 M H₂SO₄,pH=0）,respectively,and has excellent long-term stability.In addition,as the air cathode catalyst of zinc air battery,the 5%-Ir-MnO₂ modified battery also showed excellent performance.The specific capacity can reach 655.4 m A h g^-1 and 792 m A h g^-1 in alkaline and neutral media,with cycling stability up to 120 h and 200 h,respectively.（2）Using 3D Cu foam（CF）as the substrate and copper source,we in situ grew copper hydroxide nanorods and precipitated manganese ions onto it.Cu₂S-MnS spherical nanocomposite material was obtained after the hydrothermal vulcanization.Then,amporous Rh（OH）₃was introduced onto the surface.The microstructure and composition were confirmed by various characterizations.It can be concluded that the introduction of MnS and Rh species has greatly improved the performance of the catalyst.The target catalyst has excellent hydrogen evolution and oxygen production performance under alkaline conditions.As both anode and cathode electrode materials for electrocatalytic water splitting,its performance is superior to PtC/CF||RuO₂/CF modified one.