Construction,Preparation And Properties Of Anode Catalysts For Direct Methanol Fuel Cells Based On Liquid Metal

In recent years,liquid metal（LM）has attracted much attention for its excellent properties such as fluidity,high electrical conductivity,thermal conductivity,stretchability,self-healing ability,biocompatibility and recyclability,especially for its unique electronic structure and highly dynamic surface properties,which give it unique potential for catalytic applications.Therefore,the design and construction of new composite materials based on liquid metals to broaden the catalyst types and enhance the catalytic performance has become a new strategy for catalytic material design.Among many new clean energy conversion devices,direct methanol fuel cell（DMFC）has become one of the focal points of research in the field of new energy because of its advantages of high energy conversion efficiency,low operating temperature,cleanliness and environmental protection.However,the development of DMFC is currently facing many bottlenecks,especially its high cost of anode catalyst,low catalytic activity and poor resistance to neutrophilicity,which affect its large-scale application.In response to the above challenges,this work selects gallium-based LM as the main research subject,and tries to use its strong reduction and low-temperature mobility to design and prepare a series of LM-Pt composite structure of methanol oxidation（MOR）catalysts by means of the potential difference between LM and Pt using electric coupling replacement.The results of the study show that through the existence of electron transfer and strong interactions between LM elements and Pt,the Pt-based catalyst poisoning problem is changed by forming p-d orbital hybridization to alter the Pt surface electronic environment,resulting in an effective enhancement of the catalytic activity of the material in both acidic and basic catalytic media.The main studies are as follows.（1）Three LMs,Ga,EGa In（Ga 75.5 wt%,In 24.5 wt%）,and EGa In Sn（Ga 68.5wt%,In 11.5 wt%,and Sn 10.0 wt%）,were selected as precursors and reducing agents,respectively,to prepare LM-Pt catalytic materials with hollow or porous structures by the electric coupling substitution method,which can improve the electronic structure of Pt surface while increasing the exposure of active sites.The LM-Pt catalytic materials with hollow or porous structures were prepared by the electrocouple substitution method to improve the electronic structure of Pt surface while increasing the exposure of active sites.The effect of the ratio between LM elements and Pt on the catalytic activity of MOR was investigated systematically,and it was shown that the LM-based composite catalysts showed good MOR catalytic activity under acidic and alkaline conditions.Among them,the catalytic activities of Ga-Pt₂,Ga In-Pt₃ and Ga In Sn-Pt₄catalysts were preferred,reaching 318.6,308 and 634.74 m A/mg _Pt mass specific activity and 21.2,21.2 and 21.6 m A/cm² area specific activity under acidic media,respectively.1245.9,1036.1 and 1777.1 m A/mg _Pt mass specific activity under alkaline media,respectively.These are higher than those of commercial Pt/C catalysts.（2）The MOR catalysts with LM@rGO-Pt trilayer composite structure were designed and constructed.Firstly,the optimized precursor liquid metal Ga particles with small particle size,homogeneous size and stable structure were obtained by introducing surfactant;subsequently,Ga@rGO core-shell structure with reduced graphene（rGO）coating was generated on the surface of Ga to further improve its stability and catalytic activity;finally,Pt monomers on the outer surface of Ga@rGO to form Ga@rGO-Pt three-stage composite catalysts.After process optimization,the mass specific activity and area specific activity of Ga@rGO₂₀-Pt₃ were 24.04 m A/cm² and 438.74 m A/mg _Pt,and the Active area is 78.4 m²g_Pt^-1.respectively,under acidic conditions,and the current density of 21.62 m A/mg _Pt was still maintained after 2 h of chronoamperometric testing,showing better catalytic activity.Under alkaline conditions,the area specific activity and mass specific activity were 24.06 m A/cm² and 1495.29 m A/mg _Pt,respectively,and still maintained a current density of 142.12 m A/mg _Pt after 2 h chronoamperometric current test which was 7 times higher than that of commercial Pt/C catalysts.This three-layer composite structure is proved to be beneficial to increase the electron transfer rate of the catalysts,and can effectively improve the stability and corrosion resistance of the catalysts.（3）A low-cost Ga-CuPt ternary alloy catalyst of LM-CuPt type was designed and constructed by introducing Cu elements in a sequential substitution method.The effects of reduction order and Pt loading on the MOR catalytic activity of Ga-CuPt were investigated,and the Ga-Cu₂Pt₃ catalyst was optimized to have a good catalytic performance.Under acidic conditions,its mass activity was 334.9 m A/mg _Pt,which was2.1 times higher than that of commercial Pt/C catalysts,and its area specific activity was 13.04 m A/cm²,which was 1.8 times higher than that of commercial Pt/C catalysts,and its stability was 11.92 m A/mg _Pt,under basic conditions,Also superior to commercial Pt/C catalysts its mass specific activity was 696.82 m A/mg _Pt,and its stability reached 11.02 m A/mg _Pt.It has been proved that the introduction of low-cost transition metal Cu not only affects the structure of catalyst,but also effectively transfers electrons between Pt and Cu and Ga.The formation of Ga-CuPt alloy catalyst can change the electronic structure of Pt,reduce the adsorption strength of-CO_ads on the surface,and contribute to the desorption of-CO_ads,so as to effectively improve the problem of catalyst poisoning.