| Scientists are looking for a clean,renewable energy source to replace fossil fuels because of the limited fossil energy reserves and the environmental pollution of greenhouse gases from their combustion.Hydrogen is considered to be a good candidate for its high combustion heat and clean combustion products(water).Electrolysis of water is one of the cleanest and most efficient methods which can generate hydrogen.However,there are still some problems in hydrogen production by electrolysis of water.Electrolysis of water includes oxygen evolution reaction(OER)of the anode and the hydrogen evolution reaction(HER)of the cathode.Many expensive precious metal catalysts have been used to catalyze hydrogen evolution reactions(precious metal Pt,etc.)and oxygen evolution reactions(RuO2,IrO2,etc.)due to the slow kinetics(especially OER).The high price limited the practical promotion of water electrolysis.Loading a precious metal on a non-metallic base material to reduce the precious metal content as much as possible is one of the solutions which can solve the problem.More active area can be exposed to increase catalytic activity by reducing the size of precious metal particle.The other solution is to find non-precious metal catalyst materials which has excellent catalytic properties of water electrolysis.In this paper,different types of high-activity catalysts for electrolysis of water were designed and synnthesized.The hydrogen evolution and electrolysis performance of these catalysts were studied as follows:(1)OsCl3·3H2O,HAuCl4·4H2O and silicon nanowires(SiNWs)were used as raw materials to obtain Os-Au-Si ternary system complex for hydrogen evolution.The material was characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and transmission electron microscopy(TEM)to obtain structural information.Electrochemical tests show that when the current density is 10 mA·cm-2,the overpotential is 59 mV,which can be compared with 40%commercial platinum carbon(47 mV).When the overpotential is greater than 170 mV,the HER performance exceeds commercial platinum carbon.With the Tafel slope of 25 mV·dec-1,the catalyst exhibits excellent stability during electrochemical tests up to 30,000 s.(2)Using Fe(NO3)3·9H2O,Co(NO3)2·6H2O,Cu(NO3)2·3H2O,thioacetamide,ethylenediamine,1-butanol as raw materials,the precursor is obtained by hydrothermal method.The precursor was washed,dried and calcined in vacuum to obtain a three-dimensional flower-like structure of Co9S8-CuS-FeS ternary metal sulfide.X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),N2 adsorption-desorption(BET),scanning electron microscopy(SEM)were used to characterize the structure of Co9S8-CuS-FeS ternary metal.The OER performance of Co9S8-CuS-FeS ternary metal sulfide as anode electrode material was tested,indicating that the catalyst exceeded the commercial ruthenium oxide(RuO2)in current density.The overpotential is 0.289 V and the Tafel slope is 79 mV·dec-1 when the current density is 10 mA·cm-2.In addition,the catalyst has a stable OER catalytic performance for up to 50,000 s.(3)Precursors were obtained by hydrothermal method,using Co(NO3)2·6H2O,Cu(NO3)2·3H2O,carbon dots(CDs),urea,ethylenediamine and isopropanol as raw materials.After washing and drying,the final product CoO-Cu-CDs was obtained by calcined in vacuum.The catalyst was characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS).The electrochemical current test showed that the current density of the OER catalyst exceeded the commercial cerium oxide.When the flow density was 10 mA·cm-2,the potential is 0.289 V and the Tafel slope is 82 mV·dec-1.What’s more,it exhibits OER performance superior to commercial ruthenium oxide after up to 50,000 s. |
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