Design And Preparation Of High Stability And High Activity Oxygen Electrode Catalyst

Pt/C catalyst is a common catalyst for proton membrane fuel cells.However,commercialization of PEMFCs has been hampered by the high cost of Pt catalysts,sluggish kinetics of the oxygen reduction reaction?ORR?,and insufficient durability from Pt catalysts.Therefore,we have synthesized the durability of Pt/TiN and Pt/TiC catalysts and PtNi/C catalysts through a sample route.This paper combines theory and experiment to explore the titanium compound which can replace the carbon black carrier,and the experimental and theoretical research on the preparation of low Pt catalyst PtNi/C,which provides a basis for the design of enhancing the electrochemical performance of the catalyst.Anchoring effect for Pt/TiN and Pt/TiC catalysts:the weak interaction between Pt and supports is the primary roadblocks for durability catalysts of ORR process.The stability differences between the Pt/TiN,Pt/TiC and Pt/C catalysts have been studied using experiments and first principles calculations.Pt/TiN?Pt/TiC?catalysts were synthesized via the reduction of TiN?TiC?and H₂PtCl₆·6H₂O using ethylene glycol.The stabilities of the prepared Pt/TiN?10%?and Pt/TiC?5%?catalysts were examined at room temperature using accelerated durability tests?ADT?compared with Pt/C?20%?).The results shows after CV scans for 1000 cycles,the ECSAs of Pt/TiC and Pt/TiN catalysts decreased to¹3%and²2%,respectively,of the initial ECSA,while 57%ECSA of Pt/C?20%?was lost.Additionly,the TEM images clearly suggests that the Pt particles remained small in size,with well dispersed TiN and TiC.Even the durability test before and after,the specific activity?SA?and mass activity?MA?are 0.273 mA cm^-22 to 0.260 mA cm^-22 and0.141 mA mg^-1 to 0.105 mA mg^-11 for Pt/TiN catalysts,respectively,implying that the TiN support enhanced the ORR activity of Pt.The SAs for Pt/TiC were 0.130 to 0.127 mA cm^-2,and MAs were 0.085 to 0.072 A mg^-1.The experimential results show that TiN and TiC supports are suitable for anchoring the Pt particles and can also be alternative supports for electrocatalysts.And DFT calculations shows the smaller distortion energies of Pt₁₃cluster and larger the interaction between Pt-TiN and Pt-TiC systems.Besides,a larger overlap and a suitable energy match are observed between the Pt-d and TiN-p?TiC-p?states,which result in easier electron transfer between these states,thus forming the Pt-N-Ti?Pt-C-Ti?bond rather than the C-Pt bond.The electron localization domains of Pt-N,and Pt-Ti are more localized towards the Pt core.However,for TiC,the Pt atoms only bind with the C atoms.Therefore,the Pt/TiN and Pt/TiC can become the most activity and durability among the catalysts.The research for PtNi/C catalyst with low Pt content:PtNi/C catalysts are synthesized by solvothermal reaction using Pt?acac?₂ and Ni?acac?₂,N,N-dimethylformamide as reductant.The PtNi/C catalysts show the best performance for the ORR when the ratio of Pt and Ni alloy is 1:1.The half-wave potential of the PtNi/C catalyst is 0.88 V,which is 40mV more positive than the 20%Pt/C commercial catalyst?0.84 V?.The MA of the PtNi catalyst is?0.20 A/mg?twice the commercial Pt/C catalyst?0.119 A/mg?;the SA is 0.382mA/cm² which is 5.5 times higher than the commercial Pt/C catalyst?0.071 mA/cm²?.After 1000 cycles of accelerated aging cyclic voltammetry,the PtNi catalysts exhibit a significant enhancement in stability for ORR with only a 8%drop in ECSA.Density functional calculations was used for?111??110??311?plane of Pt and PtNi nanoparticles,respectively.It was found by calculation that the degree of overlap for the charge density and the size of the HOMO orbital for Pt₁Ni₁ are increased,which showed that electron transfer easily arises among the Pt₁Ni₁ catalyst.Therefore,the Pt₁Ni₁ catalyst is the best active ratio for ORR being in agreement with experiment for the ORR.