Preparation And Electrochemical Properties Of Nickel And Carbon Based Flexible Composite Electrodes

Fuel cells and supercapacitors,as efficient energy storage and conversion devices,have been widely applied currently.NaBH4 and CH3OH with high hydrogen content are safer and easier to preserve than liquid hydrogen,which are promising renewable fuel for fuel cells.For both fuel cells and supercapacitors,electrode material is an important factor And the preparation process of an electrode highly affects its performance.Conventional preparation method of electrode is commonly coating a slurry of active substance,conductive agent and binder on metal substrate.Unfortunately,the metal substrate is difficult to be wound and bent.Besides,the application of binders will reduced the utilization of active substance.Considering this,flexible binder-free electrodes arise at the historic moment which can overcome the disadvantages of low catalyst ustilization caused by the common coating method and the poor electrochemical performance of the electrode.With the rapid development of the wearable electronic device,the flexible electrodes have attracted much attention recently.In this paper,flexible nickel-carbon composite electrodes are prepared by coating,impregnation,drying,pasting and electrodeposition methods using filter paper and flexible sponge,plastic as substrates.The structure of the electrodes is investigated by SEM,TEM,XRD,Raman,FT-IR and ICP.The electrochemical oxidation and supercapacitive performances of the flexible nickel-carbon electrode are characterized by cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS)and chronoamperometry(CA).Firstly,the filter paper,A4 paper and plastic are used as the substrates and 8B pencil covered graphite layer and double-sided tape bonded carbon nanotubes(MWNTs)are served as conductive agents.After Ni film is electrodeposited on the conductive substrates,the NiPd,NiAu and NiPt films are obtained by replacement.Among them,the flexible PdNi film-graphene-filter paper(PNGF)hybrid electrode exhibits high electrocatalytic activity and stability due to the synergistic effect of PdNi and the good ability of hydrogen adsorption on the graphite coated paper.The oxidation current density on PNGF is 385 mA cm-2 at a potential of-0.3 V in 2 mol L-1 NaOH and 0.1 mol·L-1 NaBH4.The oxidation current density on the flexible A4-8B-Ni thin film-Au(ABNiAu)hybrid electrode is 180 mA cm-2 at a potential of-0.2 V in 50 mmol L-1 NaBH4.The current density on the flexible NiPt film-MWNTs-plastic(PMNP)hybrid electrode at a potential of 0 V in 0.1 mol dm-3 NaBH4 solutioncan reaches up to 750 mA cm-2.A flexible MWNT modified sponge nickel hybrid electrode(MSNi)is prepared by two simplye steps.Firstly,a conductive framework of sponge modified by carbon nanotubes(MWNT)is built throug a dipping-drying method.Then nickel nanoparticles are deposited on it to obtain the final electrode.The catalytic activity of MSNi electrode for CH3OHbelectrooxidation is studied by cyclic voltammetry,chronoamperometry and electrochemical impedance spectroscopy.The MSNi possesses a unique three-dimensional porous structure and a high water adsorption capacity and no binders are involved during the preparation process.Moreover,the MSNi displays a high electrocatalytic performance of 23 mA(cm-2 mg-1)at a potential of 0.5 V in 0.5 mol L-1 CH3OH.Using sponge as a template and sterol as a carbon source,a three-dimensional porous carbon framework(CF)is prepared by oxalic acid polymerization and solidification processes.After that,polyaniline nanowires are coated on the CF to synthsize the CF supported polyaniline nanowires(CF-PANI)electrode.In this work,different electrodeposition conditions are investigated to explore their effects on the morphology and electrochemical performance of polyaniline.Desirably,CF-PANI presents high capacitive performance,high energy and power densities,good rate capability and cyclic stability due to its unique three-dimensional porous structure and good electric conductivity.Furthermore,the asymmetric supercapacitor assembled with CF-PANI and CF electrodes presents a high energy density of 44 W h kg-1 at a power density of 800 W kg-1.