The Preparation Of Ni-Mo Alloy In Ionic Liquid And Its Catalytic Properties For Hydrogen Evolution

The traditional electrodepositon techniques of Ni-Mo alloys are bascialy takenplace in aqueous solution. Thus, hydrogen embrittlement of the materials cannot beavoided, which may affect the properties and practicality of materials.Therefore, ionicliquid solvent is utilized instead of using aqueous solvent in the experiment toelectrodeposit Ni-Mo alloys on the coper substrate by orthogonal experiment. Thehydreogen evolution activity were determined by cathode polarization curves andelctrochemical impedance spectrom (EIS) in6mol/L NaOH solution.The optimum process of Ni-Mo alloys electrodeposition on Cu substrate is asfollowing:c((NH4)2MoO4)=0.3mol·L-1, c(NiCl)=0.15mol·L-1, j(current density)=3.2A dm-2,T(bath temperature)=55℃. The morphology and structure of the assynthesized coatings under the best conditions were characterized by SEM and XRDrespectively. SEM images show that the coatings are composed of uniformaccumulated particles and EDS analysis reveal that mass percentage of Mo in thecoating is about5%。XRD pattern indicate that the prepared coatings are ofnanocrystalline structure with average crystallites sizes of2.2nm. Polarization Curvesindicate that when the current density of hydrogen evolution reaches100mA/cm2, thehydrogen evolution potential of Ni-Mo alloy deposited in ionic liquid has a positivelyshift of nearly100mV,180mVcompared to Ni-Mo deposited in aqueous solution andNi deposited in ionic liquid repectively,and a positively shift of about250mVcompared to pure Ni electrode, thus showing good performance for hydrogenevolution. EIS test show that Ni-Mo alloys electrodeposited in ionic liquid possessmuch smaller reaction impedance than pure Ni metal.By changing the substrate of deposition, orthogonal experiment design methodwas used to electrodeposit Ni-Mo alloys in ionic liquid. The results indicated that thebest deposition condition can be described as c((NH4)2MoO4)=0.2mol·L-1,c(NiSO4)=0.35mol·L-1, j(current density)=5A dm-2, T(depositon temperature)=30℃. SEM images show that the carbon-felt fibers alloy are almost coated withNi-Mo alloys.The coatings whose mass percentage of Mo is5.12%present athree-dimensional structure of the fiber network. Polarization curves indicate that thehydrogen evolution potential of C-Ni/Ni-Mo alloy deposited in ionic liquid has a positively shift of nearly108mV compared to C-Ni elctrode and about557mVcompared to carbon felt electrode under the current density of100mA/cm2.