Study On Ag Based Oxygen-Evolving And Pt Based Catalytic Dehydrogenation Catalysts For Hydrogen Production

Hydrogen which is abundant in storage and rich in sources can be obtained by one-time,twice and reproducible resources.Hydrogen and oxygen can be transformed into electricity(or heat energy)and water without any pollution.Hydrogen can be produced from water.So hydrogen is regarded as a promising material to meet energy demand in the future and has attracted the attention of many countries.While the efficient and low-cost hydrogen production technique is one of the important premises for hydrogen application.In the paper,a novel Ag-B;oxygen-evolution catalyst was electrochemical deposited on the ITO substrate in situ under mild conditions(near-neutral aqueous solutions,room temperature,and atmospheric pressure).The electrochemical properties of the Ag-Bi oxygen-evolution catalyst were investigated in more detail.A WO3/Ag-Bi oxygen-evolution catalyst that combines an Ag-Bi catalyst with W03 was generated.The WO3/Ag-Bi oxygen-evolution catalyst is superior to Ag-Bi oxygen-evolution catalyst when it comes to the performance of the oxygen-evolution rate and overpotential.Silver oxide based oxygen-evolution catalyst was explored in the different electrolyte solution contain Ag+ ion.An expected Ag-Ci oxygen-evolution was obtained in the electrolyte(pH=8.3)that was a dilute NaOH solution while CO2 was supplied continuously with Ag+ ion.The catalytic activity of Ag-Ci oxygen evolution catalyst prepared under different conditions was studied in more detail.Highly disperse Pt/UiO-66 catalysts were prepared by loading platinum nanoparticles onto the UiO-66 MOF with high thermal stability.Their catalytic properties over liquid organic perhydrofluorene(PHF)have been elaborately investigated.The primary contents and results are as follows:1.Under mild conditions(near-neutral aqueous solutions,room temperature,and atmospheric pressure):a novel Ag-Bi oxygen-evolution catalyst was generated by controlling the electrolysis potential in the 0.1 mol/L K2B4O7 solution(pH=9.2)with Ag+ ion.The composite and oxygen-evolution performance of Ag-Bi catalyst were investigated.The results indicated the oxygen-evolution rate in situ was 10.75 ?mol/h and the oxygen-evolution overpotential ?=290 mV at the current density of 1 mA/cm2.W03 was used to modify Ag-Bi oxygen-evolution catalysts by in situ deposition on an ITO,which formed a novel WO3/Ag-Bi catalyst.This catalyst showed excellent catalytic activity for water splitting:the oxygen-evolving overpotential decreased from 318 mV to 290 mV at a current density of 1 mA/cm2;the oxygen evolution rate increased from 10.75 ?mol/h to 12.34 pmol/h.2.The electrolyte solution plays an important role in preparing oxygen-evolution catalyst in situ,and act as a proton acceptor and ligand for oxygen-evolution catalyst.An Ag-Ci oxygen-evolution was obtained in the electrolyte(pH=8.3)that was a dilute NaOH solution while CO2 was supplied continuously with Ag+ ion.However,the Ag-Ci oxygen-evolution catalyst differed from reported amorphous oxygen-evolution catalyst and was crystalline materials.The temperature of the electrolyte has a great impact on the performance of Ag-Ci catalyst,the crystal type of Ag-Ci and catalytic activity depends on temperature.When the temperature of the electrolyte varies from 25? to 70?:the oxygen-evolution rate increase from 4.47 ?mol/h to 13.49?mol/h and the oxygen-evolution overpotential decreased from 474 mV to 280 mV.3.Highly pure metal organic framework UiO-66 is synthesized by varying synthetic conditions.UiO-66 sample is composed of individual and octahedrally shaped 200 nm.UiO-66 isnanocrystals.The size of the uniform crystals was about 150 thermally stable up to 500? under nitrogen atmosphere.Pt/UiO-66 catalysts were prepared by loading platinum onto the UiO-66 MOF using the incipient wetness impregnation method by hydrogen reduction.The uniform dispersion and small particles with the size mainly between 2 and 3 nm were found for the catalyst samples with Pt/UiO-66.It is worth noting that matching the cavity size is important for preventing the particle from further growing and aggregation.Investigation over the dehydrogenation properties of perhydrofluorene is carried out on each reduced Pt/UiO-66 catalysts.The 5wt.%Pt/UiO-66 catalyst,with a Pt particle diameter of about 2.5 nm,resulted in a maximum PHF dehydrogenation capacity of 6.54 wt.%with the PHF dehydrogenation conversion over 97%after 310 min of reaction.The 5wt.%Pt/UiO-66 reaction rate is significantly higher than that obtained for 5wt.%Pt/?-Al2O3 in the early reaction period.