Study On The Preparation And Electro-catalytic Performance Of Pd-based Binary Alloy Nano-Particles As Cathode Catalysts For DBHFC

At present,the cathode catalysts of DBHFC are mainly based on platinum or platinum based alloys.But the expensive price and resource scarcity of platinum greatly limit its use.Therefore,it is necessary to seek cheap alternatives to reduce costs.Noble metal Pd,the same group with Pt,is cheaper than Pt for its higher earth reserves relatively.It has been widely used as catalyst in fuel cell,such as electrocatalytic oxidation of methanol,NaBH4 and others,for its good physical and chemical stability and catalytic properties.In this paper,the catalytic activity and stability of Pd-Ni and Pd-Co as DBHFC cathode catalysts for H2O2 electric-reduction reaction were studied respectively.This work is beneficial to technical development and commercialization of fuel cell.The main research contents are as follows:(1)The Pd-Ni/C catalysts,with different total metal content(20%,30%,40%)and different Pd-Ni mass ratios,were prepared by a two-step impregnation reduction route.The effects of palladium nickel reduction sequence and the Pd reduction reaction time(1h,2h,3h,4h)on the catalyst were studied.The above catalysts were characterized by TEM and XRD.Their electrochemical performance were measured in different electrolyte(NaOH:0.25mol/L,0.5mol/L,0.75mol/L,1mol/L,1.25mol/L)and different reactant(H2O2:0.04moI/L,0.06mol/L,0.08mol/L,0.10mol/L,0.12mol/L,0.15mol/L)solutions at different temperatures(10?,15?,20?,25?,30?,35?).The characterization results show that all the Pd-Ni/C alloy are the face-centered cubic structure,the particles can be well distributed on the carbon support,and the diameter of Pd-Ni binary catalyst particles is about 4.5nm.The electrochemical performance results show that the introduction of Ni into Pd/C can improve the catalytic activity effectively.The best mass ratio of Pd-Ni alloys with 40wt%and 30wt%of Pd-Ni are Pd30-Ni10/C and Pd20-Ni10/C respectively.At 25?,the two catalysts showed good catalytic activity in 0.5mol/L NaOH and 0.06mol/L H2O2 mixed solution.(2)The different proportions of Pd-Co/C binary alloy nano-catalysts were prepared by a one-step impregnation-reduction method.The effects of different reduction reaction time(1.5h,2h,2.5h,3h)on the catalyst structure and properties were investigated respectively.All catalysts were characterized and their electrochemical performances were tested in the mixed solution(0.5mol/L NaOH+0.06mol/L H2O2).The results show that Pd-Co/C alloy catalyst was also a face centered cubic structure,the particles can be well distributed and the diameter of Pd-Co binary catalyst particles is about 4.4nm.When Co was introduced into the Pd/C to form Pd-Co/C alloy,the catalytic activity of the catalyst was visibly improved.The catalytic performance of the Pd-Co/C alloy is slightly better than that of Pd-Ni/C when they have the same alloy proportion.The optimal mass ratio of 40wt%Pd-Co alloys is Pd30-Co10/C.(3)The Pd30-Ni10/C and Pd30-Co10/C were used as the cathode catalysts respectively,and the Pt/C(40wt%)was used as the anode catalyst to assemble DBHFCs,the performance of the two fuel cell were tested under the same condition.The results show that the corresponding cell power densities were 90.6mW/cm2 and 80.91mW/cm2 respectively.That means the Pd-Co and Pd-Ni binary alloy both played a good catalysis for H2O2 reduction in the DBHFC,and the catalytic performance of Pd3o-Co10/C is better than that of Pd30-Ni10/C.