Controllable Synthesis And Performance Of Fuel Cells Based On PdBi Nanocrystals

Fuel cells have attracted much attention due to their high efficiency,high energy density,and extremely low pollution emissions.Pd-based nanocatalysts are commonly used to catalyze the cathodic oxygen reduction reaction（ORR）of direct methanol fuel cells（DMFCs）because of having many advantages.However,the price of precious metal Pd is expensive.It is an advantageous way to drop cheap non-precious metal to reduce the using of Pd.This paper aims to reduce the catalyst cost in this way,synthesize nanocatalysts with controllable structure,and improve the electrocatalytic performance of the catalysts by tuning the surface electronic structure.In this work,interface-rich Au-doped PdBi branched one-dimensional（1D）alloyed nanochains assembled by sub-6.5 nm particles have been prepared,exhibiting an ORR mass activity（MA）of 6.40 A mg_Pd^–1 in an alkaline medium.The MA of PdBi Au nanochains is 46 times and 80 times higher than that of commercial Pt/C(0.14 A mg_Pt^–1)and Pd/C(0.08 A mg_Pd^–1).The MA of PdBi nanochains also reaches5.71 A mg_Pd^–1.The doping of“active auxiliary”Au not only improves the mass activity but also greatly improves its stability in oxygen reduction reaction.The analysis of the structure-function relationship indicates that the enhanced performance of PdBi Au nanochains is attributed to integrated functions of surface defect-rich 1D chain structure,improved charge transfer capability,downshift of the d-band center of Pd,and the synergistic effect derived from“Pd-Bi”and/or“Pd-Au”dual active sites.Notably,the PdBi Au nanochains exhibit high in-situ carbon monoxide poisoning resistance and high methanol tolerance.In actual DMFC device tests,the PdBi Au nanochains enhance power density of 140.1 m W cm^–2（in O₂）/112.4 m W cm^–2（in air）and durability compared with PdBi nanochains and Pt/C.Furthermore,Pd_0.58Bi_0.37Cu_0.05 and Pd_0.60Bi_0.35Ag_0.05 nanochains were formed by doping a trace amount of Cu or Ag to PdBi nanochains by one-step solvothermal method.The factors affecting the nano-chain structure of Pd_0.60Bi_0.35Ag_0.05 were obtained through experimental exploration of control variables.The experimental results show that the main factors are the addition of Bi（NO₃）₃ and the regulation of surfactant F-127.In the ORR performance test,the mass activities of Pd_0.58Bi_0.37Cu_0.05and Pd_0.60Bi_0.35Ag_0.05 were 5.62 and 5.80 A mg^-1.And the doping of Cu or Ag can fully enhance its stability for ORR,which may be attributed to the existence of lattice strain.Meanwhile,Pd_0.58Bi_0.37Cu_0.05 and Pd_0.60Bi_0.35Ag_0.05 are electrochemical catalysts with dual properties.As anode catalysts,their catalytic activity and stability for formic acid oxidation are better than Pt/C and Pd/C.