Preparation And Performance Of Anodic Catalysts For Direct Methanol Fuel Cells

In order to solve the problems of the increasing global energy demand and the escalating climate warmth and environmental pollution,it is urgent to find more clean alternative energy sources and develop efficient energy conversion devices.Among different types of sustainable energy systems,direct methanol fuel cell(DMFC)has a simple structure and superior properties,such as high theoretical energy density,high energy conversion efficiency,small size,low operating temperature,and environmental friendliness.In addition,fuel methanol is cheap and easy to obtain,transport and store.It is one of the most promising energy generators and can be widely used in automotive power supplies and portable electronic equipments.At present,one of the main factors restricting the development of DMFC is that its cost is too high-the use of precious metal catalysts.And the other is that it is easy to be poisoned by CO and the electrocatalytic efficiency is reduced.Therefore,current researches have focused on Pt-based catalysts with higher performance and lower loading,and non-precious metal(Ni,Co,etc.)catalysts as alternatives to Pt for methanol oxidation.On the one hand,a new carbon support was selected to improve the activity of Pt catalyst.On the other hand,non-precious metal nickel was investigated,and an improved nickel-based catalyst(Ni3S2/CFs)was prepared.And the characterization and electrochemical performance were studied.(1)Based on the effect of the support on the performance of the catalyst,Pt nanoparticles supported on Co-N co-doped reduced graphene oxide(Pt/Co,N-RGO)were prepared.The morphology,structure and composition were characterized by XRD,XPS and TEM.The electrochemical performance was studied by using cyclic voltammetry(CV)and chronoamperometry(CA)methods.The results show that Pt/Co,N-RGO exhibited higher activity and better durability for methanol electrooxidation than Pt/N-RGO and commercial Pt Ru/C,mainly due to the co-doping of Co and N elements in the support and the interaction between the support and Pt nanoparticles.(2)Ni/CFs were prepared by depositing metallic nickel on carbon fibers(CFs)substrate,and then were hydrothermally sulfurized by TAA in a stainless steel autoclave to obtain nickel sulfides(Ni3S2/CFs).The electrocatalytic performance of the as-obtained Ni3S2/CFs catalysts at different hydrothermal temperatures was investigated.The catalysts were physically characterized by using XRD,XPS,SEM and TEM and the electrocatalytic performance was investigated by using CV,CA and electrochemical impedance(EIS)methods.The results show that the nickel sulfide(Ni3S2/CFs-170)prepared at 170? exhibited the best electrocatalytic performance.In 1.0 M KOH + 1.0 M CH3 OH solution,the current density of methanol oxidation on Ni3S2/CFs-170 at 1.60 V is about 657.1 m A cm-2;In the stability test,the peak current density at the 500 th cycle on Ni3S2/CFs-170 decreased from 657.1 m A cm-2 to 502.2 m A cm-2 with a decrease of 23.6%;The result of EIS show that Ni3S2/CFs-170 exhibited smaller charge transfer resistance than Ni/CFs and other Ni3S2/CFs obtained at 150?,160? and 180?.The above reason may be due to the porous structure beneficial to diffuse reactants and smaller charge transfer resistance.