| Since 2020,major economies in the world have put forward the expected time for "Peak carbon dioxide emissions",China has more determination to achieve "carbon neutrality" by 2060.Researchers hope to use technologies such as photovoltaics,hydrogen production,fuel cells,and carbon dioxide catalytic conversion to emulate nature and completely consume greenhouse gases directly or indirectly produced by human activities.As the link between cycles,fuel cells,metal-air batteries and other devices are playing an increasingly important role in this profound transformation of the world’s energy forms.Oxygen reduction reaction is a key rate-controlling step in the electrochemical reaction involved in such devices,and it is urgent to develop a cheaper,greener,stable,and efficient catalyst than traditional Pt/C to ensure long-term efficient operation of the device.At present,non-precious metal oxygen reduction reaction catalysts(NPMC)based on polymer-derived carbon have received widespread attention.The main difficulties of its industrial production and commercialization are:(1)The polymerization reaction mechanism is complicated,and it is difficult to judge the kinetics,mass transfer,and heat transfer processes in a homogeneous/heterogeneous system;(2)The distribution of metal active centers is not uniform,and the catalytic activity which performed is difficult to complete.Solving the above-mentioned problems is crucial to the promotion of catalyst manufacturing and related energy devices.The high-gravity technology with the high-efficiency micro-mixing system provided using the rotating packed bed(RPB)as the core has been proved to have a reliable strengthening effect on the partial polymerization reaction and the polymerization devolatilization process.The impregnation method has potential value as the production process of M-N-C type non-precious metal oxygen reduction catalyst.In this thesis,the main steps of catalyst synthesis are strengthened separately by using rotating packed bed,and obvious effects have been obtained.Main tasks as follows:(1)Preliminary exploration of the polymerization reaction kinetics of 2,6-diaminopyridine was carried out,and it was confirmed that the remaining ratio of raw materials changed with the reaction time.The rotating packed bed was used to strengthen the initial polymerization process,so that the reaction system rapidly changes from a single liquid phase to an average oligomer dispersion,and the subsequent polymerization process was completed in a beaker.After 180 minutes,the conversion ratio of 2,6-diaminopyridine molecules increased by about 9%compared with the beaker test.In the subsequent 540 minutes,the conversion rate only increased by 0.050%,which proved that the reaction time was shortened to 180 min after the polymerization process was strengthened by the rotating packed bed.(2)Cyanamide was added to participate in the polymerization of 2,6-diaminopyridine to adjust the base structure of polymer-derived carbon materials;transition metal Mn was doped to catalyzes the graphitization process of carbon materials during pyrolysis,without changing the pyrolysis Under the conditions,the limiting current density of the DAP-based catalyst was increased,and finally the specific surface area of the catalyst is 715.671 m2/g.When tested in 0.1 M KOH electrolyte,the half-wave unit reached 0.883 V and the current density reached 3.840 mA/cm2,The stability of each is better than that of Pt/C catalyst.The test of zinc-air battery showed that the open circuit voltage reached 1.320 V and the power density reached 141.120 mW/cm2.(3)The process of polymer hydrothermal adsorption of transition metals was completed in a rotating packed bed with three times the reaction system.Under these conditions,the content of loading Fe in the catalyst prepared was had a significant increase,which matched the results of linear sweep voltammetry.The half-wave potential reached 0.889 V,and various types of electrochemical stability were better.In the zinc-air battery test,the open circuit voltage reached 1.350 V.It maintained an average potential difference of 0.033 V when it was subjected to cyclic discharge tests of various power densities,and the stability was excellent.Its power density reaches 178.180 mW/cm2,which was had obvious advantages over commercial Pt/C. |
