Surface Modification Of Pt/C With Ozone And Catalysis In Methanol Electro-oxidation

With the development of national economy,energy shortage and environmental pollution are becoming more and more serious.Direct methanol fuel cells have many advantages and have attracted the attention of many researchers.However,the slow methanol oxidation kinetics and low toxicity resistance of the anode catalyst hinder the commercialization of direct methanol fuel cells.Up to now,precious metal platinum is the main active component of anode catalyst.Therefore,it is necessary to conduct oxidation modification on the surface of the carrier to produce a large number of oxygen-containing functional groups on the surface to improve the dispersion of platinum and reduce its particle size distribution.However,traditional acid-base treatment,strong oxidant treatment and graft modification not only accompany with tedious post-treatment procedures,but also destroy the inherent morphology of the carrier.It is very meaningful to find an effective,convenient and green surface oxidizer to treat the catalyst carrier,so as to improve the activity and stability of the catalyst.In this paper,Pt-based catalyst was synthesized by immersion method and surface modification was carried out by ozone.Through TEM,Raman,XPS,XRD,BET,FT-IR,electrochemical measurement and other technologies,the influence of ozone treatment temperature and time on the surface characteristics of the support was systematically studied,as well as the comparison between ozone treatment and several traditional oxidation methods,and the following research results were obtained:1.With the increase of ozone treatment temperature,the content of oxygen-containing functional groups on the surface of carbon black increased from10.6%to 18.2%,the particle size distribution of platinum nanoparticles decreased from 2.34nm to 2.04nm,and the agglomeration of Pt nanoparticles was significantly improved.When the temperature was 140℃,Pt nanoparticles were most evenly dispersed.In addition,with the increase of ozone treatment temperature,the activity and stability of the catalyst were improved.The peak current density of methanol oxidation of the catalyst reached a peak of 17.48 mA cm^-2 when the temperature was 140℃,and the stability of the catalyst was also the best.However,when the treatment temperature was higher than 140℃,the catalyst performance decreased.2.With the increase of ozone treatment time,the content of oxygen-containing functional groups on the carbon black surface increased from5.2%to 10.9%,the particle size distribution of platinum nanoparticles decreased from 2.40 nm to 2.07 nm,and the agglomeration of Pt nanoparticles was significantly improved.When the time was 30 min,Pt nanoparticles were most evenly dispersed.Moreover,with the increase of ozone treatment time,the activity and stability of the catalyst were improved.The peak current density of methanol oxidation of the catalyst reached a peak of 12.70 mA cm^-2 at the time of 30 min,and the stability of the catalyst was also the best.However,when the treatment time was more than 30 min,the catalyst performance decreased.3.In order to investigate whether ozone is suitable for the treatment of other carbon materials in the preparation of methanol electrocatalytic oxidation catalyst,we choose to use ozone oxidation to modify 3D carbon nano-sheets.In addition,ozone treatment was compared with nitric acid,hydrogen peroxide and other oxidation methods,and the results showed that the ozone-treated catalyst produced the most oxygen-containing functional groups with the content of 7.7%without destroying the original morphology of the carrier.Compared with other catalysts,the peak current density of methanol oxidation is 85.30 mA cm^-2,and the stability of catalyst is the best.Ozone treatment process is also relatively simple and safe,showing the superiority of ozone treatment.