The Crystal State Control Of Pd-Ni-P Nanoparticles And Their Catalytic Performance In Alcohol Electrooxidation Reactions

To meet the widespread commercial use of direct alcohol fuel cells,it is of great significance to develop low price and excellent electro-catalysts for anodic oxidations.Among Pd-based catalysts,Pd alloys mixed with non-noble metal or nonmetal atoms,can effectively reduce the cost of catalyst,leading to excellent catalytic performance,such as,high activity and durability.This paper selects Pd,Ni,and P to form a ternary composites Pd-Ni-P nanoparticles.By changing the mole ratio of the precursors,Pd-Ni-P nanoparticles were fabricated with different crystal forms using a one pot solvothermal reduction method.Pd/Ni composition dependent morphologies（amorphous versus crystalline）,electronic properties,and catalysis of the bimet-P were studied.To investigate the correlations between composition with catalysis of the Pd-Ni-P ternary composite nanoparticles（Pd-Ni-P NPs）,electro-oxidation of methanol and ethanol（MOR and EOR）were carried out in an alkaline medium（1.0 M alcohol and0.5 M KOH）.Using three electrode electrochemical devices,the electro-oxidation was monitored by cyclic voltammetry（CV）,scan constant voltage chronoamperometry（I-T）,and slow scanning linear scanning method（LSV）.Regular physical characterizations were carried out with transmission electron microscope（TEM）,high power transmission electron microscopy（HRTEM）,X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）,energy spectrum analyzer（EDS）,inductively coupled plasma emission spectrum instrument（ICP-MS）,and diffraction and infrared spectrum（FTIR）.The control synthesis morphologies（amorphous versus crystalline）of Pd-Ni-P NPs with tunable Pd/Ni ratio,and loaded on XC-72 activated carbon,then for electrochemical testing.The catalysis tests in alcohol electrochemical demonstrated that the amorphous Pd₃₈Ni₂₆P₃₆/C NPs has the best catalytic performance in alcohol.In particular,the stability of electrooxidation of ethanol was greatly improved.After i-T 4000 s,the specific activity was approximately 6.63 times compare to 10%Pd/C.After 400 cycles of CV,the activity was approximately 4.42 times that of 10%Pd/C.In order to further study on the composition,morphology and the catalysis of Pd-Ni-P NPs,choosing the optimal catalyst of amorphous Pd₃₈Ni₂₆P₃₆/C NPs as the research object,three kinds of Pd₃₈Ni₂₆P₃₆/C-X（X=400T,500T,600T）were fabricated by increasing the calcination temperature and Pd/Ni composition with a constant mole ratio,the electrochemical results show that the crystalline Pd₃₈Ni₂₆P₃₆/C-600 T exhibits the best performance,especially the electrooxidation stability,far better than the commercial Pd/C,therefore that Pd/Ni composition predominally determinates the catalytic activity rather than the morphology,maybe ascrible to the Pd-Ni bimetallic effect and the electro-deficiency of Pd due to the formation of Pd-P bonds.This work would promote the application of bimetallic-P compouds in alcohol fuel cell as anode catalyst.