The Preparation And Investigation Of Ternary Alloy AuNiCu Anode Catalyst For Direct Borohydride Fuel Cell

Direct borohydride-hydrogen peroxide fuel cell?DBHFC?,one of the fuel cells which is consisted of alkaline aqueous solution of Na BH₄ as fuel and acid H₂O₂ as oxidant.In theory,the totally oxidation of BH₄^-at anode can tranfer eight electrons.However,the practical number of electrons can not reach to 8due to the borohydride hydrolysis.What's more,the borohydride hydrolysis can decrease the utilization of BH₄^-,and some security risks are produced.Therefore,the key factor for the study of DBHFC is to develop high catalytic acitivity anode electrocatalysts which can inhibit the hydrolysis of BH₄^-and promote the oxidation of BH₄^-.The catalysis of noble metal Au is relative high to the oxidation of BH₄^-,and the columbic efficiency can reach to 100% under given conditions.However,slow electrode kinetic of BH₄^-on Au anode lead to the low power output and poor electrochemical performance of the DBHFC,Au could not be the anode catalyst alone.Ni,3d transition metal,when applied to DBHFC,the polarization of the oxidation of BH₄^-is low,the open circuit potential is negative,but the performance of Ni catalyst is poor,which could not be the anode catalyst alone as well.Cu,another 3d transition metal,which shows high catalytic activity towards the direct oxidation of BH₄^-,promote the hydrolysis of BH₄^-at the same time.In order to adequately develop the advantages of each metal,our research group has studied the electrooxidation performance of on Au Ni catalysts and Au Cu catalysts,and found the addition of Ni or Cu could obviously improve the catalytic properties of Au,the dosage of Au could also reduced.In order to deeply investigating the effect of the addition of 3d transitionmetal,this article has studied the addition of Ni and Cu simultaneously based on the study of our research group,investigate the effect of the electrochemical oxidation behavior of BH₄^-when additing Ni and Cu simultaneously.First,a series of carbon-supported Au?Au₁Cu₁?Au₁Ni₁?Au_x Ni₁Cu₁?x= 0.2,0.5,1,1.5,2?alloy nano-particles have been synthesized by a polyol reduction method.The morphology and structure are investigated by transmission electron microscopy?TEM?and X-ray diffraction?XRD?.The results of physical characterization show that the different atomic ratio alloy nano-particles have a good dispersion,the nano-particles were distributed on the carbon uniformly,and the average size is between 8 nm and 17 nm.Second,Electrochemical characterizations are performed by cyclic voltammetry?CV?,linear scan voltammetry with rotating disc electrode?LSV RDE?,electrochemical impedance spectroscopy?EIS?,chronopotentiometry?CP?,chronoamperometry?CA?,and fuel cell test.The results show that among these catalysts which have been prepared,the catalytic activity of ternary alloy catalysts and bimetallic nanoparticles were higher than pure catalyst Au/C,when the ternary catalysts and bimetallic nanoparticles all have 50% amount of the Au elements,the ternary catalysts Au₂Ni₁Cu₁/C shows higher catalytic activity than bimetallic nanoparticles Au₁Cu₁/C and Au₁Ni₁/C,and the different content of Au elements in the catalysts shows different performance.According to the comparison of all the catalysts,Au₁Ni₁Cu₁/C shows the highest catalytic activity.Based on the datas of chronoamperogram,the number of BH₄^-oxidation on the Au₁Ni₁Cu₁/C is 7.6,which is higher than Ni₁Cu₁/C.The DBFC using Au₁Ni₁Cu₁/C as anode electrocatalyst and Pt mesh?1cm2?as cathode electrode obtains the maximum anodic power density as high as 68.14 m W cm-2,which is8.6 times higher than Ni₁Cu₁/C in the same condition at 20 o C.In the paper,the electrocatalytic performance of ternary alloy catalysts Au_x Ni₁Cu₁/C is better than bimetallic catalysts Au₁Cu₁/C?Au₁Ni₁/C and purecatalyst Au/C,this may be reason form electronic effect or bifunctional effect.?1?Electronic effect: adding Cu or Ni into Au element may changed the electronic band structure of Au,decreased the adsorption energy of the reaction intermediate.For example,the BH3OH—species can be easier adsorbed onto the surface of Au,making the reaction more easily to happen.?2?Bifunctional effect:according to the experimental result form this article,the catalytic activity of Au_x Ni₁Cu₁/C is higher than Au₁Cu₁/C and Au₁Ni₁/C,this may be the result of the addition of Ni and Cu simultaneously,which enhanced the coulombic efficiency of the catalysts.When the atomic ratio of metal is Au:Ni:Cu = 1:1:1,the bifunctional effect is the best,the catalytic activity of the catalyst is the highest.