Enhanced Electrochemical Catalysis Of Bimetallic AgNi@Polyaniline Nanocomposite Modified Pt On Formic Acid-Formate Oxidation

The physical and chemical properties of a bi-metal or multi-metal nanoalloy are different from those of a single-metal on account of a synergy among the metals.Pt,Pd,Ag,Au,Ni,Co,Cu are usually employed to fabricate the multi-metals.Researchers have been focusing on AgNi nanoalloy because of its excellent features,such as simply processing,stable chemical property,good biocompatibility,as well as low cost.The reports on the application of AgNi nanoally as an electrochemical catalyst have increased over in recent years.However,the nanoparticles are needed to be supported or prevented with another material because they are active and easy to remove from their usuall locality.Conjugate polymers,such as polyaniline or polypyrrole,are famous for their stability and adjustable conductivity.It is supposed the polymers should not only prevent the particles from losing,but might take part in the synergy among every component,and further improve some properties of the nanoalloy.Herein,bimetal AgNi nanoalloy was prepared through a liquid phase reduction method.Further,an oxidant-induced polymerizing method was ultilized to coat AgNi nanoparticles with polyaniline(PANI).The fabricated AgNi@PANI composite was characterized by XRD,FE-SEM,TEM,HRTEM,UV-vis,FT-IR,TGA,XPS and Raman.Results show that Ag and Ni have formed nanoalloy particles.The synergy between the two metals is help for reducing the diameter to 4-5 nm.The bimetal and the conductive PANI in the core-shell AgNi@PANI nanocomposite show their own chemical features,and no a new chemical bound is formed between them.At the same time,AgNi nanoparticles are beneficial to enhancing the conductivity and thermostability of PANI.Further,we fabricated AgNi@PANI modified Pt(AgNi@PANI/Pt)electrodes,studied their electrochemical activities in formic acid-formate solution.Results indicate the electrodes present an excellent electrocatalysis on formate oxidation in a certain range of formate cuncentration.The forward peak current density up to 30.7 mA cm-2 can be measured when the molar ratio of AgNi alloy is 1:0.5.In addition,the electrochemical stability of PANI/Pt electrodes has been obviously improved because of the existence of AgNi nanoparticles.At 1200s,the current of AgNi@PANI/Pt electrode is almost 8 times as high as that of PANI/Pt electrode in an acidic formate solution,according to chronoamperometry results.Meanwhile,our researches on the electrooxidation mechanism of formic acid-formate system indicate that AgNi@PANI nanocomposite can promote the direct oxidation of formic acid and formate to CO2,rather than the indirect oxidation to toxic CO and CO-like intermediates.That is AgNi@PANI is helpful to prevent Pt from intermediates poisoning.The result also provides direct electrochemical evidence to the third oxidation pathway of formic acid-formate system.