Preparation Of Mn-based Oxide Catalysts And Their Electrocatalytic Applications

There are many kinds of metal oxides,low cost,low toxicity,and various oxidation states and crystal structures.Therefore,they have become important research objects in heterogeneous catalysis,such as manganese-based oxides.This paper proposes that the sol-gel method and hydrothermal method can be used to control the preparation of MnO₂ catalyst,and the method of introducing oxygen vacancies(OVs)on the surface of MnO₂ catalyst can effectively improve its catalytic activity for ORR and OER reactions.At the same time,this work proposes that the MnO_x catalyst is uniformly loaded on the metal titanium membrane to construct an electrocatalytic membrane reactor(ECMR)to effectively degrade phenol wastewater and provide a new idea for the efficient treatment of refractory industrial wastewater.The main research contents are as follows:(1)The?-MnO₂ and?-MnO₂ catalysts were synthesized by hydrothermal method,and the 1D?-MnO₂ and?-MnO₂ were synthesized by H₂ reduction method and air calcination method respectively.Oxygen vacancies(OVs)are generated on the surface of the nanorods,and the catalysts were used to oxygen reduction reaction(ORR)research.The research results show that,compared with the air treatment catalyst,?-MnO₂-H₂-350?-10 min and?-MnO₂-H₂-350?-10 min after H₂reduction shows better catalytic performance.The?-MnO₂-H₂-350?-10 min ORR performance is the best,can reach the initial potential 0.93 V,half-wave potential 0.73V,limiting current-4.7 m A cm^-2.At the current density of 5 m A cm^-2,the OER catalytic activity reached an overpotential of 410 m V.(2)Two kinds of one-dimensional nanorods MnO_x LNRs?MnO_x SNRs and two-dimensional nanosheets MnO_x NSs catalysts with three different morphologies supported on the titanium film were prepared by hydrothermal method.The results show that the two-dimensional MnO_x NSs/Ti electrode exhibits high electrochemical active area(4.1 cm^-2),and the electrochemical activity is the best among the three electrodes.(3)The 2D MnO_x NSs/Ti membrane electrode is used as the anode to construct ECMR to catalyze the degradation of phenol wastewater.By optimizing the process parameters of the electrocatalytic membrane reactor(current density,residence time,content of reactant phenol),the optimal conditions of the membrane reactor were obtained:at a temperature of 25?,a current density of 1.4 m A cm^-2,and a residence time of 14 min,phenol wastewater concentration 2 mmol/L and electrolyte Na₂SO₄concentration 14.4 g/L,the removal rate of phenol reached 99.9%.