| Hydrogen is considered to be an ideal alternative to fossil fuels due to its high energy density and environmental friendliness.Among the traditional method to produce hydrogen,electrochemical water splitting has attracted widespread attention due to its simple operation,low pollution,and high efficiency.In recent years,a large number of non-precious metal catalysts have been studied to replace precious metal materials such as RuO2/IrO2 and Pt.Nonetheless,some shortcomings exist in most of the materials,such as poor electrical conductivity and sample shedding during testing,which reduce the catalytic performance of the catalysts.Therefore,it is particularly important to develop a non-precious metal material with excellent mechanical stability and high conductivity as a highly efficient catalyst for electrocatalytic water splitting.In this dissertation,grass-like Ni/Cu nanosheet arrays,Ni-P/Fe?OH?3-Cu nanotubes and grass-like Ce-doped Ni-S@Cu composites with high electrical conductivity and excellent mechanical stability were generated in situ by electrochemical methods using copper foam as the substrate and the copper source.In addition,the influences of some factors on the catalytic performance were explored,including the deposition time,the current density,and the electrolyte concentration.The main content is summarized as follows:1.Grass-like Ni/Cu nanosheet arrays were successfully grown on copper foam by a simple galvanostatic electrodeposition route.Experiments showed that the as-deposited grass-like Ni/Cu nanosheet arrays possessed excellent electrocatalytic activity for hydrogen evolution reaction?HER?.In 1 M KOH solution,the nanosheet arrays only required a low overpotential of 38 mV to deliver a current density of-10 mA cm-2.Simultaneously,the present catalyst also presented a high durability.After continuously catalyzing for 50 h at a current density of-30 m A cm-2,the overpotential had no obvious increase.The above outstanding electrocatalytic activity should be attributed to the special grass-like structure of the catalyst,which exposed more effective active sites,promoted electrolyte penetration and facilitated gas diffusion.More importantly,the present Ni/Cu/CF electrode could be used as cathode in a two-electrode setup for the overall water splitting,employing the RuO2/CF as anode.In 1.0 M KOH,the Ni/Cu/CF//RuO2/CF electrode only needed a cell voltage of 1.51 V to reach a current density of 10 mA cm-2.2.Ni-P/Fe?OH?3-Cu nanotube arrays were successfully prepared on copper foam as efficient OER catalysts,with iron nitrate as the iron source,nickel chloride and sodium hypophosphite as the nickel and phosphorus sources,respectively.In 1.0 M KOH solution,the as-obtained hybrid electrocatalyst required only a low overpotential of 271 mV to achieve a current density of 20 mA cm-2 with a small Tafel slope of 57.7 mV dec-1.After1000 CV cycles at the scan rate of 100 mV s-1,the overpotential of the catalyst hardly increased;and after continuously catalyzing for 130 h at a current density of 20 m A cm-2,the potential only increased from 1.527 V to 1.541 V,implying that the as-obtained hybrid electrocatalyst possessed excellent cycle stability and long-term stability.The above outstanding electrocatalytic activity should be ascribed to its special tubular structure and the synergic action between Ni-P alloy and Fe?OH?3 nanotubes.In addition,the presence of elemental copper,which was formed by the electrochemical reduction of Cu?OH?2,also enhanced the catalytic performance due to its excellent electrical conductivity.3.A mild electrochemical route was designed for successful preparation of Ce-doped Ni-S@Cu nanosheet composites on copper foam as an oxygen evolution catalyst.Some parameters affecting the catalytic performances of the final product were investigated,such as the deposition time and the doping amount of cerium nitrate.Electrochemical tests showed that the electrode prepared by doping 0.2 mmol Ce?NO3?3·6H2O owned the best catalytic activity,which only required 240 mV of overpotential to reach a current density of 50 mA cm-2.After the catalyst was continuously utilized at a potential of 0.56 V?vs.Hg/HgO?for 35 hours,the current had no obvious increase.It is worth noting that the as-prepared Ce-Ni-S@Cu/CF electrode and the Ni/Cu/CF electrode obtained in the first section were separately used as the anode and cathode in a two-electrode system for overall water splitting.At a current density of 50 mA cm-2,Ni/Cu/CF//Ce-Ni-S@Cu/CF only needed a battery voltage of 1.58 V to achieve overall water splitting. |
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