Research On The Electrocatalysis Of Biomass-based Non-platinum Fuel Cell Catalysts

The environmental pollution caused by the abnormal global climate change and the excessive use of fossil fuels has had a serious impact on the development of human society.As an efficient and environmentally friendly energy conversion device,fuel cells can effectively improve energy use efficiency and reduce environmental pollution.Therefore,they have received special attention.The slow kinetic process of the cathode oxygen reduction reaction（ORR）is one of the main bottlenecks in the research of proton exchange membrane fuel cells（PEMFCs）.In commercial applications,Pt-based catalysts are generally used to improve the slow kinetic reaction rate of cathode.However,the high price,poor stability and poor resistance to methanol toxicity of Pt-based catalysts have greatly limited the development of fuel cells.In order to solve the key problems in fuel cells,an ionic liquid swelling chemical activation method was proposed to prepare porous carbon materials based on biomass.This porous carbon material has good ORR electrocatalytic performance and remarkable stability.The specific research contents are as follows:（1）Cotton was used as biomass precursor,and three different types of activators（Na OH,Zn Cl₂,H₃PO₄）were used to activate and preprocess it.The biomass mixture with elasticity was obtained,and then the porous carbon materials with developed pore structure were prepared by direct pyrolysis and carbonization.The best activator and experimental conditions were explored by electrochemical test.The experimental results showed that the specific surface area of DC-800 prepared by Na OH activation was the highest,reaching 1,257.57 m² g^-1,and its electrocatalytic performance of oxygen reduction was the best.The limiting current density of this porous carbon material in ORR reaches 4.3 m A cm^-2,the initial potential reaches 0.83 V,and its stability is much better than commercial Pt/C.（2）In order to study the influence of ionic liquid swelling chemical activation method on the oxygen reduction performance of porous carbon materials.Na OH/urea ionic solution was used to fully swell cotton fibers and partially dissolve the surface of cotton fibers on the basis of the previous chapter,and then the nitrogen-doped porous carbon materials were prepared at different carbonization temperatures.Physical characterization and ORR performance tests show that when the carbonization temperature is 800℃,the specific surface area of the optimized NDC-800 porous carbon material reaches 2,183.76m² g^-1,and it has a more developed micro pore structure.This nitrogen-doped porous carbon material rich in three-dimensional mesoporous structure exhibits excellent electrocatalytic performance,with an initial potential of 0.90 V and a limiting current density of 4.81 m A cm^-2.In general,the electrocatalytic performance of the catalysts is close to that of commercial Pt/C catalysts.（3）Finally,the transition metal Fe element was introduced into the biomass porous carbon material.The cotton was activated and doped with Na OH/urea/iron citrate ionic liquid to prepare iron-nitrogen co-doped porous carbon materials.The effect of doping with different mass ratios of iron citrate on the electrocatalytic performance of the samples was explored.Electrochemical tests showed that Fe NDC-0.05-800 had the best ORR catalytic activity when the mass ratio of Na OH/urea/iron citrate was 7:12:0.05,the initial potential of Fe NDC-0.05-800 reached 0.87 V,and it showed excellent stability.