Research On Modified Carbon Supported Pt-Based Metal Catalyst For Fuel Cell

Fuel cell is an integral part of new clean energy power generation equipment,which has the characteristics of clean and environmentally friendly,and efficient energy conversion.Fuel cells have not been widely applied because of the slow reaction rate on the cathode side,which requires catalysts to accelerate the reaction.At present,Pt/C catalyst is still the preferred catalyst for the fuel cell.However,the existing Pt/C catalysts have many problems to be solved,such as the high cost of the catalyst due to high consumption of platinum,easy peeling and dissolving of active components under high temperature and pressure,and low activity.To solve the problems,the structure and morphology of platinum-based metal nanoparticles（NPs）,the active center of the catalyst,were studied extensively.However,most researchers do not pay much attention to the effect of carbon support on platinum metal nanoparticles and catalysts,so the catalyst can not play its due potential.The purpose of this paper is to figure out the problems of carbon supported platinum based metal catalysts.The research is based on the"carbon support modification-interaction enhancement-active component structure regulation-performance improvement"of research thought.According to the characteristics of different carbon supports,targeted modification is carried out to give new structure and functional characteristics to carbon supports,optimize their physical structure and regulate the interaction between modified carbon materials and Pt NPs.After modification,the key factors such as crystal structure,electronic structure,dispersion,and particle size of Pt NPs were regulated.The catalyst’s electrochemical performance and the membrane electrode assembly’s polarization performance（MEA）were improved comprehensively.In addition,a variety of modification strategies were compared,and 40 wt%Pt/C catalysts with the same metal components were prepared.Under the condition of the same Pt loading,the increase of Pt content can significantly reduce the thickness of the catalyst layer and improve the performance of MEA.In this context,the catalysts were prepared at the gram level.It provides a new perspective on the gram level synthesis and popularization of fuel cell catalysts under laboratory conditions.The main research contents are as follows.1.Vulcan XC-72 carbon black was covalently and non-covalent modified by H₂O₂ and CTAB,and Pt₃Ni NPs were supported on the dual modified carbon black（DMC）by ethylene glycol reduction method to prepare Pt₃Ni/DMC catalyst.Compared with carbon black,DMC’s structure and functional properties were optimized,the mesoporous structure was maintained,and the specific surface area was increased.In addition,the improved functionalization of DMC can improve the crystal structure,electronic structure,and dispersion of Pt₃Ni NPs supported on DMC,which is beneficial for the oxygen reduction reaction.Compared with the catalyst made of carbon black,the electrochemical performance of Pt₃Ni/DMC catalyst has been enhanced in all aspects.The electrochemically active area（ECSA）and mass activity（MA）of Pt₃Ni/DMC catalyst is 130 m²/g and 0.56 A/mg _Pt,which were improved by 110%and 409%compared with JM Pt/C,respectively.Pt₃Ni/DMC catalyst showed good stability,and its ECSA and MA decreased only 39.5%and 29.1%after the stability test.In the performance test of membrane electrode（MEA）,the maximum power density（MPD）of Pt₃Ni/DMC is 450 m W/cm².2.Ordered mesoporous carbon（OMC）was obtained by filling mesoporous template SBA-15 with glucose.OMC was covalently modified by ammonium persulfate（APS）.Pt₃Cu NPs were supported on the modified mesoporous carbon by ethylene glycol reduction to prepare Pt₃Cu/MMC catalyst.After APS modification,the modified ordered mesoporous carbon（MMC）maintained the advantage of the original mesoporous structure and highly ordered pores.Compared with OMC,the oxygen-containing functional groups in MMC greatly enhance the degree of functionalization of carbon materials,strengthen the interaction between carbon materials and Pt₃Cu NPs,and promote the positive regulation of electronic structure and crystal structure Pt₃Cu NPs by carbon materials.In addition,the domain-limiting effect of ordered mesoporous channels and the anchoring effect of functional groups promote the excellent dispersion of Pt₃Cu NPs.The performance test results show that the ECSA and MA of Pt₃Cu/MMC catalyst reached 65.2 m²/g and 0.58 A/mg _Pt,respectively,which were improved by 31%and 380%compared with JM Pt/C catalyst,respectively.Under the stability test,the loss of ECSA and MA of Pt₃Cu/MMC was only 9.45%and 12.06%,which was much lower than that of the unmodified catalyst.The MPD result of Pt₃Cu/MMC catalyst is 641 m W/cm²,which has the highest activity among the ordered mesoporous carbon catalysts of the same type.3.The in-situ polymerization modification of conductive polymer ethylene dioxythiophene（EDOT）on Ketjenblack EC-300J was realized by APS.Modified carbon black（PEDOT@C）was supported with Pt NPs synthesized by an improved Na BH₄ reduction method,and then 40 wt%Pt/C catalysts were prepared.Compared with unmodified carbon black,the functional properties of PEDOT@C are improved.In addition,PEDOT coupled with carbon black through its wealthy functional groups promoted the strengthening of the interaction and enhanced the dispersion of high content Pt NPs.The electrochemical test results show that the PEDOT modification strategy helps improve the catalytic performance of the catalyst.Under the dual action of the excellent conductivity of PEDOT and the optimization of the structure and function of carbon black,the ECSA of Pt/PEDOT@C reaches 114.28 m²/g,and the MA is 0.142 A/mg _Pt.In addition,the coating of PEDOT on carbon black has a protective effect on carbon black,which significantly enhances the stability of the Pt/PEDOT@C.The loss of ECSA and MA is only 8.33%and 9.8%,respectively.In the polarization performance test of MEA,the MPD result of Pt/PEDOT@C is 1470 m W/cm²,higher than that of an unmodified catalyst.4.Dual modified EC-300J carbon black,modified ordered mesoporous carbon,and PEDOT modified EC-300J carbon black were supported with the same loading of Pt NPs to synthesize 40 wt%Pt/C catalysts.By comparing,the Pt/DMC catalyst made of dual modified EC-300J carbon black showed the best electrochemical performance.In addition,to realize the gram level synthesis of the catalyst under laboratory conditions,the peristaltic pump was used to control the titration rate of metal precursor and reductant solution.Thus the high uniformity of Pt NPs synthesis environment is achieved.The repeatability of the Pt/DMC catalyst was verified,and various specifications such as 1,5,and10 g were prepared.The MPD values of 1,5,and 10 g catalyst are 1805,1580,and 1380 m W/cm²,respectively.In a word,by optimizing and modifying the carbon support,their structure and chemical characteristics were optimized,the interaction was strengthened,the chemical properties of metal nanoparticles were regulated,the electrochemical performance of the catalyst was improved,and the repeatable and batch preparation of the catalyst was realized.The carbon support modification strategy provides a new and valuable idea for the large-scale application and development of carbon-supported platinum-based metal catalysts for fuel cells.