Evolution of nanoscale amorphous, crystalline and phase-segregated PtNiP nanoparticles and their electrocatalytic effect on methanol oxidation reaction.

The design of amorphous noble metallic nanoparticle electrocatalysts is an important fundamental and applied research challenge because their surface is rich in low-coordination sites and defects which could act as the active sites in various catalytic processes. Here we describe new findings on the amorphous platinum-nickel-phosphorous nanoparticles supported on carbon black (PtNiP(a)/C) and the comparison between their catalytic activity and that of the nanoscale crystalline and phase-segregated PtNiP nanoparticles. The nanoscale amorphous, crystalline and phase-segregated catalysts were probed as a function of surface composition, particle size, and thermal treatment conditions using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, selected area electron diffraction and electrochemical characterization. The results provide the experimental evidence in support of nanoscale amorphous, crystalline, and phase-segregated PtNiP nanoparticles evolution dependence on the catalyst synthesis temperature. More importantly, the results of the electrochemical performance investigation showed that the amorphous structure has not only better catalytic activity for methanol oxidation but also stronger tolerance to carbon monoxide poisoning compared to the crystalline and phase-segregated structure. Besides, the thermal control of the formation of nanoscale amorphous, crystalline and phase-segregated structured catalysts provided the opportunity for establishing the correlation between the nanoscale phase structures of the catalysts and their electrocatalytic activity in methanol oxidation reaction, which plays an important role in developing highly active electrocatalysts for direct methanol fuel cells.