The Synthesis Of Transition Metal Phosphates And The Investigation Of Electrochemical Properties

Supercapacitors have been considered as a novel energy storage devices,due to its short recharging period,long cycling life,high power density,renewable energies and environment.As another of the most promising mobile powers,fuel cells possess varies advantages,such as high energy density,simple method in fuel storage and transportation,few environmental pollutions.As the key material of two devices,electrode materials and catalysts play important role in overall performance and applications.Transition metal?specified Co,Ni,Mn in this article?oxides/hydroxides/sulfides exhibited excellent performances and remarkable application value in many fields.However,transition metal phosphates are obviously rare reported in the sides of preparations and performances.Herein,as novel supercapacitive material,cobalt nickel phosphates with different Co/Ni ratios were constructed through a mild hydrothermal method,then formed uniform honeycomb-like mesoporous structure via a facile dehydration process.The cobalt nickel phosphates,the Co/Ni ratios of 1:3,exhibiting high specific capacitance of 1409.8 F g-1 at 0.25 A g-1.Moreover,home-made carbon material with porous structure synthesized via activated buns with KOH,used as negative electrode to assemble an asymmetric supercapacitor with Co0.86Ni2.14?PO₄?₂ as the positive electrode.The as-prepared battery exhibits high energy density of 45.8 Wh kg-1.In the side of electrocatalysis,we report firstly the synthesis of manganese phosphate nanomaterial via a facile hydrothermal reaction used as the ORR catalyst.We controlled the process of nucleation and growth through choosing different phosphorus sources,such as Na3PO4,Na2HPO4,NaH₂PO4,and improved the performances of crystallinity and stability by anchoring reduction graphene oxide.The as-prepared catalyst material of manganese phosphate nanosheets show high ORR performance nearly the commercial 20 wt.% Pt/C in 1 M KOH solution.Finally,to verify the influence of pH values for the manganese phosphate crystal,we choose NH4 Cl as buffering agent to control efficiently the pH values of solution and dissolution-recrystallization in the hydrothermal process.The results show that the pH values are significant for the synthesis of the manganese phosphate material,and the performance of flake manganese phosphate is the best at a pH level of 8.