Controllable Synthesis And Electrocatalytic Performance Of Platinum-based High-index Crystalline Faceted Catalysts

With the development of today’s society,the problems of declining traditional fossil energy reserves and environmental pollution have attracted attention.The new energy source Direct Ethanol Fuel Cell（DEFC）has been widely researched because of its advantages of easy fuel availability and green efficiency.However,the diffusion of DEFC is hindered by the fact that the active component of the catalyst in DEFC relies mainly on the precious metal Pt,which is facing problems of higher cost,lower catalytic performance and lower atomic utilisation.According to the study,it was found that Pt-based catalysts with high index crystalline orientation with a large number of defective atoms such as steps and kinks on the surface showed excellent catalytic performance.In this thesis,we address the problems of high cost,catalytic performance for ethanol and low atom utilisation of noble metal Pt nanocatalysts.The XC-72R carbon black-loaded Pt₁Co_x/C high-index crystalline facets nanocatalysts were prepared in one step by hydrothermal method using polyvinylpyrrolidone（PVP k-25）as dispersant and reducing agent,glycine as surface control agent and co-reducing agent,and modulating the molar ratio of Pt-Co metal precursors by in situ growth.HRTEM analysis of the crystalline facets showed that the exposed high-index crystalline facets of the Pt₁Co_1/3/C nanocatalyst mainly consisted of{410},{510}and{610}crystalline facets;The growth pattern of Pt₁Co_1/3/C nanocatalyst grains was found to vary from’sphere-like’to cubic to concave with a high index crystallographic orientation.The electrocatalytic performance of the Pt₁Co_1/3/C nanocatalysts showed the highest electrocatalytic activity with an electrochemically active surface area of 18.46 m²/g,a current density of 48.70 m A/cm² for the ethanol oxidation peak,a steady-state current density of 8.29 m A/cm² and a potential of 0.610 V for the CO oxidation peak.The results of the formation conditions of Pt₁Co_1/3/C high index nanocatalysts showed that glycine influenced the formation of high index crystalline facets,indicating that glycine was a key condition for the synthesis of Pt₁Co_1/3/C high index crystalline nanocatalysts.It was also shown that catalysts synthesised on PVP-functionalised carbon carriers have better catalytic performance than untreated ones,and have higher microstructural endoconcave selectivity and superior electrochemical performance.The amount of carbon carrier occupation has an influence on the synthesis of Pt₁Co_1/3/C high index crystalline surface catalysts.When the XC-72R carbon black accounted for 10%of the total catalyst,the synthesised Pt₁Co_1/3/C high index crystalline surface catalyst had the highest morphological structure selectivity and the best catalytic performance for ethanol.In order to develop multiplexed high-index crystalline facets catalysts,Pt-Mn-Fe system nanocatalysts with high-index crystalline facets orientation were prepared by hydrothermal method,and the in situ etching effect was achieved by individually adjusting the addition of Fe metal precursors to the multiplexed catalysts while maintaining the high-index crystalline facets morphology.The high index crystallographic surfaces exposed by the Pt-Mn-Fe catalysts were mainly found to include{410},{510},{610},{710}and{810}crystallographic surfaces,which were characterised by XRD,TEM and electrochemical workstations.The electrocatalytic performance characterisation showed that the Pt-Mn-Fe multi-nanocatalyst with high exponential crystal plane orientation had an electrochemically active surface area of 6.68m²/g,a catalytic oxidation peak current density of 28.83 m A/cm² for ethanol,a steady-state current density of 1.16 m A/cm² and a potential of 0.610 V for the CO oxidation peak.At 16.8 m L,microstructural characterization revealed that the Pt-Mn-Fe high-index crystalline surfaces became rough,and crystal surface analysis revealed that the exposed high-index crystalline surfaces included{410},{510},{610},{710}and{810}crystalline surfaces.The results of the electrocatalytic characterisation show that the in situ etched Pt-Mn-Fe catalyst has a better catalytic oxidation performance for ethanol,the Fe content is further increased and the microstructure of the catalyst shows a"gully"cracking on the surface of the Pt-Mn-Fe nanograins and the disappearance of the typical high index morphology of the inner concave.