Rare Earth Constructed Pt-free System And The Application Research For Anode Reaction Of Fuel Cells

As large-scale applications of fuel cells have been hindered by extensive use of Pt-based catalysts,it goes without saying that the future of fuel cells technology depends heavily on developing more efficient,stable,and economical Pt-free catalysts.At present,Pd,Ni and Ir metal have been recognized as promising substitutes to Pt for anode reaction of fuel cells.However,it is difficult to obtain excellent activity and stability for mono-metallic catalysts.It is reported that metal oxide and alloy can be used as promoters to enhance the performance of the primary metal.And then,they have good prospect in the catalyst.In addition,due to their unique electronic structure and a variety of catalytic properties,rare earth elements have also been attracted much atttention in the field of electrocatalysis.Therefore,it is an effective strategy to achieve the commercialization of fuel cells by introducing the rare earth into primary catalytic metals to form a“rare earth constructed Pt-free system”for anode rection.This study mainly focuses on the synthesis of high efficiency and low cost Pt-free catalysts for fuel cells.The thesis makes full use of the promoting effect of metal oxide and alloy,as well as the excellent properties of rare earth elements,using Sm and Ce to prepare“rare earth constructed Pt-free system”.At first,the promoting effect of hybrid metal oxide was investigated to Pd in glucose oxidation reaction.Subsequently,the promoting effect of rare earth based alloy structure was investigated to Ni in urea oxidation reaction.Finally,metal oxide,alloy and rare earth elements are introduced into the catalyst,successfully constructed“rare earth based Pt-free”system for ethanol oxidation.In these three parts,the structures of as-prepared catalysts were characterized by physical measurements.And their electrocatalytic performance was also studied by electrochemical test methods.The thesis consists of three parts as follows:Part Ⅰ:Hybrid SnCoO_x oxide promoting Pd nanoparticles towards glucose electrooxidationA novel binary Sn-Co oxide promoting Pd catalyst（Pd-SnCoO_x/C）is synthesized via facile precipitation and polyol methods for glucose electrooxidation.Compared with Pd/C catalyst,as-prepared Pd-SnCoO_x/C catalyst has larger electrochemically active surface area,higher electrochemical activity and superior stability.This high catalytic performance may be attributed to the synergistic effect between binary Sn-Co oxide and Pd nanoparticles,leading to smaller size and higher dispersion for Pd-SnCoO_x/C than Pd/C.Part Ⅱ:Ni₅Sm-P/C ternary alloyed catalyst for urea electrooxidationA ternary Ni-based alloy incorporating assistive metal and non-metallic component was successfully fabricated for urea electrooxidation.The addition of Sm and P changes the electronic distribution of the Ni₅Sm-P/C and generates more active form of NiOOH,which is beneficial to the catalystic performance.Therefore,the Ni₅Sm-P/C catalyst exhibits high catalytic activity and stability for urea electrooxidation.Notably,the anodic peak current of Ni₅Sm-P/C catalyst is over 1.5times,21 times and 29 times higher than those of Ni-P/C,Ni₅Sm/C and Ni/C,respectively.Part Ⅲ:Heterogeneous Ir₃Sn-CeO₂/C for ethanol electrooxidation in acidic mediaCombination of the promoting effect of metal oxide and alloy,as well as the excellent properties of rare earth elements,an Ir₃Sn-CeO₂/C heterogeneous catalyst is designed as Pt-free electrocatalyst towards ethanol oxidation reaction in acidic conditions.Owing to the strong synergistic effect among Ir,Sn and CeO₂ components,Ir₃Sn-CeO₂/C heterogeneous catalyst exhibits higher catalytic activity and stability in comparison with commercial Pt/C,as-prepared Ir/C and Ir₃Sn/C.