Preparation And Performance Of Anodic Catalyst For Alkaline Direct Methanol Fuel Cell

Direct methanol fuel cell（DMFC）,as a device to directly convert chemical energy into electrical energy,has been widely studied due to its advantages such as high energy conversion efficiency,environmental friendliness,portable equipment,as well as easy transportation and storage of methanol.However,the high cost,vulnerable poisoning,and slow reaction kinetics of DMFC anode catalyst restrict its full-scale commercialization.Fortunately,these problems can be alleviated to some degree when the reaction is conducted in alkaline media with alkaline direct methanol fuel cell（ADMFC）.In this thesis,several effective strategies to rationally design Pt-base,Pd-base,and non-noble metal Ni-base electrocatalysts are presented and their catalytic activity,anti-poisoning performance,as well as the stability for methanol oxidation reaction（MOR）in alkaline solutions in order to overcome those intrinsic limitations of DMFC anode catalysts.In order to improve the catalytic activity and the utilization of Pt,Pt NPs were loaded on the surface of the nanofiber array.The Pd Ni catalyst was prepared by alloying to improve the anti-poisoning ability.Finally,in order to reduce the cost,Ni₃N nanosheet arrays were prepared.（1）Preparation and the MOR properties of Pt-based catalystsCore-shell Ti C@C and Ti C@CNx nanofiber arrays（NFAs）consist of highly conducting Ti C core and electrocatalytically active carbon shell or N-doped carbon shell were fabricated on Ti-6Al-4V substrate alloy by a one-step thermochemical process.The core-shell structure of NFAs endows it is an ideal scaffold for loading Pt catalysts.Herein,Pt/Ti C@C and Pt/Ti C@CNx NFAs catalysts ware obtained by loading uniform Pt NPs using a simple wet chemical method.Benefiting from the special structures of the Pt/Ti C@CNx NFAs catalyst,it drives a current density of MOR in alkaline medium as much as 6372.26 m A mg_Pt^-1,which is 4.7 times that of commercial Pt/C.（2）Synthesis and the MOR properties of Pd Ni alloy catalystsNitrogen-doped carbon coated porous Pd Ni alloy nanorods（Pd Ni@CNx）were synthesized by a simple two-step method.Firstly,the[Pd Ni/dmg₂]_nchelate was prepared by the coordination reaction between Pd（II）/Ni（II）and dimethylglyoxime（dmg）;Secondly,Pd Ni@CNx was producted by annealing the chelate in Ar/H₂（5 Vol%H₂）atmosphere at 300～500°C for 3 h.The effects of annealing temperature and the ratio of Pd/Ni on the morphology and MOR properties of the catalysts were also investigated systematically.The Pd₂Ni₁@CNx obtained at the optimal condition shows excellent electrochemical activity such as lager current density and good anti-poisoning property.Specifically,Pd₂Ni₁@CNx delivers a current density as high as 1.8 times that of commercial Pd/C.The onset potential of Pd₂Ni₁@CNx negatively shifts by 100 m V compared with commercial Pd/C in the CO stripping voltammetry cover,indicating the better anti-poisoning nature of Pd₂Ni₁@CNx after the addition of metal Ni.（3）Preparation and the MOR properties of Ni₃N nanosheet arraysA series of porous Ni₃N nanosheet arrays were prepared on a Ni foam（NF）substrate with a two-step method via nitriding Ni（OH）₂precursor grown on a NF with a hydrothermal method at different temperatures.The Ni₃N-400 obtained at the optimal condition shows a highly active and stable MOR performance with a current density of 186.15 m A cm^-2.The current density can remain 72.58%of the initial value after continuous running 20 h.