| As a new energy conversion device,fuel cell has been widely concerned because of its high fuel utilization and no pollution.Among them,Direct Borohydride Fuel Cell(DBFC)is a kind of fuel cell which uses borohydride as the fuel.As a common borohydride,sodium borohydride(Na BH4)has the advantages of high hydrogen content,high energy density and high specific capacity.At the same time,as a solid fuel,it is easy to save and transport,so it is a promising fuel.Electrode is one of the important parts of fuel cell.The catalytic activity of anode material for the electrooxidation of Na BH4 directly affects the performance of DBFC.In recent years,three-dimensional(3D)porous electrode has been a research hotspot,which has excellent gas-liquid mass transfer efficiency,and its own porous channel solid structure also helps the gas generated in the electrochemical reaction process escape rapidly.In this paper,carbon cloth(CC),carbon paper(CP)and cobalt foam(CF)were used as the electrode supports to prepare electrode materials by electrodeposition,chemical reduction and galvanic replacement methods,and their catalytic behavior for the electrooxidation of Na BH4was also studied.The morphology,composition and electrochemical properties of the electrodes were studied by methods of scanning electron microscope(SEM),transmission electron microscope(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),inductively coupled plasma optical emission spectrometer(ICP-OES),cyclic voltammetry(CV)and chronoamperometry(CA).Co(OH)2 nanoplates were loaded by electrodeposition on CC support,and then it was been impregnated in HAu Cl4 solution,the Co(OH)2-Au/CC electrode was obtained by galvanic replacement method,and the catalytic behavior of Co(OH)2-Au/CC electrode for the electrooxidation of Na BH4 was studied.In the solution containing 2.0 mol dm-3 Na OH and 0.20mol dm-3 Na BH4,the highest oxidation current density(411.1 m A cm-2)of Co(OH)2-Au/CC electrode was much higher than that of Co(OH)2/CC electrode(13.1 m A cm-2).Noble metal Au had excellent catalytic ability for the electrooxidation of Na BH4,and its introduction formed synergistic effect with Co(OH)2 and can improve the conductivity of the electrode.It was worth noting that CC was a flexible support,and its good flexibility made Co(OH)2-Au/CC electrode be hopeful to be applied in portable wearable equipment.Co(OH)2 nanoplates were grown on CP support through electrodeposition process.Then some Co(OH)2 was reduced to metallic Co in Na BH4 solution.The Co(OH)2-Co/CP electrode was obtained and used to catalyze the electrooxidation of Na BH4.The electrode after the reduction by Na BH4 still maintained 3D porous structure,which was conducive to the diffusion of BH4-in the electrode and the escape of H2 during the electrooxidation.In the solution including 2.0 mol dm-3 Na OH and 0.30 mol dm-3 Na BH4,the highest oxidation current density reached 251.7 m A cm-2.The introduction of Co can produce synergistic effect with Co(OH)2,which was helpful to improve the catalytic activity of the electrode.Co-B/CF electrode was prepared by one-step electrodeposition on CF support.The electrode showed good catalytic capacity for the electrooxidation of Na BH4 in alkaline environment.When the potential was-0.2 V and the solution containing 2.0 mol·dm-3 Na OH and 0.30 mol·dm-3 Na BH4,the oxidation current density was as high as 1685.8 m A cm-2.CF support had 3D porous structure which can make the reaction liquid spread rapidly in it,and was conducive to improve the catalytic activity of the electrode.The B in the Co-B/CF electrode was in an electron-deficient state,which can enhance the ability of the catalyst to adsorb BH4-and improve its electrocatalytic performance. |
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