Direct Methanol Fuel Cell Cathode With Nitrogen Doping Carbon Gel Load Non-noble Metal Catalyst Research

In recent years, the research of Direct methanol fuel cells （DMFC） have already made agreat progress, but the performance and cost of DMFC still have not met the need of thecommercial applications because of some technical problems, low activity of the cathodecatalysts is especially more serious, leading to the high metal loading and high cost of DMFC.The main research contents of this thesis is to develop the nitrogen doped carbon supportednon-noble metal based catalysts with low cost and better catalytic activities.Carbonization temperature and metal quantity of the Co-MF catalysts was studied. Theelectrochemical properties of the catalysts were evaluated by a rotating disc electrode （RDE）technique in O2-saturated0.5mol·L-1H2SO4solution, the catalysts showed a goodelectrocatalytic activity for oxygen reduction reaction（ORR），and the best activity wasexhibited when the carbonization temperature is800℃and the metal quantity is6wt.%in theCo-MF catalysts, the crrent dnsity is2.4mA·cm^-2at the rotation rate of1600rpm, the poresize of the catalysts is7.87nm and the specific surface area is265m²·g^-1.MR aerogels which is modified MF aerogels were prepared by using melamine, resorcinoland formaldehyde. The optimized preparation conditions are as follows: gel solution pH valueis9, the molar ratio of melamine and resorcinol is4:1and the aging time is3days, in thisconditions the specific surface area of the catalysts is502m²·g^-1, the pore size is20.34nmand the nitrogen content is13.41wt.%. The MR aerogels is amorphous porous carbon. Co wasloaded by impregnation method, influence of the carbonization temperature to theCo-MRx-CA was studied. The metal is cubic crystalline structure, cell parameter and averageparticle size increased and with increasing the carbonation temperature; Carbon in thecatalysts is spherical or columnar nanometer particles，metal particles were well dispersed,and the metal particles’ average particle size is10-20nm; The result of electrochemical testingshows that, the influence order of the carbonization temperature is800℃＞700℃＞900℃＞600℃, the catalyst Co-MR4-CA which he molar ratio of melamine and resorcinol is4:1exhibited the best electrocatalytic activity at each carbonization temperature. Co or Fe basedcatalysts（Co-MR4-CA and Fe-MR4-CA） supported on MR carbon aerogels were synthesizedthrough impregnation method，and the active center of the catalysts were preliminaryinvestigated. the metal is cubic crystalline structure, C present in C=N groups or quinonegroups, N present in pyridinic or pyrrolic structure, and Fe²⁺, Fe³⁺or Co²⁺are the dominantspecies on the surface of catalyst particles. The non-noble metal concentration is high in the catalysts, which Co and Fe is16.45wt.%and23.84wt.%respectively; Electrochemical testingshows that both Co-MR4-CA and Fe-MR4-CA have electrocatalytic activity, Co-MR4-CAexhibited the better activity at the higher rotation rate, the crrent dnsity is4.3mA·cm^-2at therotation rate of1600rpm, oxygen reduction reaction initial potential at0.5V（vs.SCE）on thecatalysts, and the reaction is occurred by four-electron-step; CN_xsuch as pyridinic, pyrrolicon the carbon surface maybe is the active center of the catalysts, and the non-noble metal isthe promotion factor under high temperature.The Co-MR4-CA and Fe-MR4-CA catalysts were used as the cathode catalyst to prepareMEAs and a single DMFC. The results showed that the higest power densities at60℃of thesingle DMFC with Co-MR4-CA and Fe-MR4-CA catalysts were39.34and38.89mW·cm^-2.