Preparation And Properties Of PtNi Alloy And Fe/N/C Cathode Catalysts

Possessed of advantages such as high specific energy and contamination free,proton exchange membrane fuel cells(PEMFCs)are functioned as a perfect energy conversion device.However,during the process of its development,high-level cost,as well as poor activity and low stability severely holds it back.Currently,platinum and platinum-based precious metals are commonly used as catalytic materials,but the high expenses of platinum-based metals which is limited storage and uneven distribution limit the industrialization process of PEMFCs.Therefore,the synthesis of low platinum or non platinum catalyst has great practical significance for reducing the platinum loaded and improving the utilization of platinum.To lower the Pt loading,this thesis synthesis highly active PtNi alloy catalyst firstly.To improve the stability of PtNi alloy catalyst,the surface of the carbon-supported platinum-nickel alloy is coated and sintered by dopamine,which effectively improves its catalytic stability.In order to further reduce the consumption of precious metal platinum and the cost of catalyst,the method of waste utilization is applied,where melamine-formaldehyde resin(MF)solid waste is adopted as a precursor to synthesize carbon-supported iron-nitrogen catalyst.The catalyst obtained has mesoporous structure and high specific surface area,and exhibites excellent performance in electrochemical catalytic activity in acidic-medium based electrochemical tests.First,to lower the Pt loading.Experiments are carried out to synthesize carbon-supported platinum-nickel alloy catalyst by adopting microwave-assisted ethylene glycol reduction method.This method has advantage of simplicity,convenient,repeatability,and could be able to prepare well-structured and uniformly distributed nano-materials(2?5nm),even more,the electrocatalytic activity is superior to commercial Pt/C(20at.%).However,it has been found that the stability is poor under accelerated attenuation test in oxygen atmosphere.With the intention to improve its catalytic stability,the alloy catalyst is coated with dopamine and sintered in nitrogen atmosphere,during the 10,000 cycles of circulation under accelerated attenuation test,the crystallinity of the as-prepared alloy catalyst only has a decline of?15 mV,while the catalyst without coating receives a decline of?65 mV under 0.8 V in its oxygen reduction performance.The carbon-supported platinum-nickel catalyst obtained shows strong predominance against commercial one,not only more cost-effective,but also much more stable.The as-prepared catalyst has high mass activity(0.49A·mgpt-1)and large electrochemical active area(ECSA)(100.5 m2·gpt-1).In order to further bring down the cost of the catalyst,we adopt melamine-formaldehyde resin solid waste as a precursor to prepare carbon-supported iron-nitrogen catalyst.Three different catalysts,BP-MF-Fe-10/10/1,BP-MF-Fe-10/10/2 and BP-MF-Fe-10/10/4,are respectively synthesized by changing the ratio of the doped iron.The electrochemical characterization shows that the onset potential of BP-MF-Fe-10/10/2 is 0.95 V,which is consistent with the high specific surface area(780.7m2·g-1)obtained by BET.This indicates that higher specific surface area will expose more active sites,which contributes to the improvement of catalytic performance.TEM characterization reveals that the iron particles are evenly distributed between the graphite carbon layers,and the proper iron conponent(10/10/2)not only gets ample access to the nitrogen-contained carbon layer,but also forms Fe/N/C structure and avoids the agglomeration of iron particles.On top of that,the half-cell performance of the synthesized low-cost Fe/N/C structure catalyst under acidic medium is close to 5%of that of the commercial one.We adopt melamine-formaldehyde resin solid waste as a precursor to prepare non-platinum catalyst.Melamine-formaldehyde resin provides rich carbon and nitrogen for the actively catalyst,which possesses visible mesoporous structure and high specific surface area.The Fe/N/C catalyst synthesized completely averts the use of precious metal platinum,resulting in the low production expenses.The method applied not only solves the recycling problem of solid waste,but also turns it into resources which are recyclable and eco-friendly.