Study On Modulated Preparation And Catalytic Properties Of The Anodic Oxygen-evolving Catalysts

Hydrogen is clean and highly efficient and is a carbon-free energy with very low environmental impact.The efficient and low-cost hydrogen production technique is one of the important premises for hydrogen application.Hydrogen by water electrolysis can be produced by simple equipment and technological process.It is friendly to environment and ecology.Hydrogen and oxygen don't need to be separated,which are produced in cathode and anode,respectively.Hydrogen production by water electrolysis is most likely to industrial application.Solar energy and wind energy are also sustainable energy.However,they are intermittent and difficult to connect electricity grid.The utilization of solar energy on a large scale requires its chemical storage.The main defects of the present hydrogen production by water electrolysis are the high costs and low energy conversion efficiency,which become the technological bottleneck and restrict the application.The novel anodic oxygen evolution catalytic technology operated under mild conditions and near neutral electrolyte environment can effectively solve this problem.However,the efficient and stable oxygen evolution catalyst is the key to realize this technology.In the paper,the novel anodic oxygen evolution catalysts are controlled to prepare by different metal precursor,matched electrolyte system,crystalline structure and modulation of the temperature.Three novel oxygen evolution catalysts?Cu-C_i,Ag-P_i and Co-C_i?are deposited on the ITO substrate in situ under mild conditions.The Ag₂WO₄ oxygen evolution catalysts with different crystal forms are prepared.The Fe-Ni Se/NF with 3D structure is prepared in situ by impregnation reaction.The structure and morphology are examined by XRD,TEM and SEM.The component and valence state of the in situ electrodeposition catalyst are investigated by EDS and XPS.The catalytic activity and stability are analyzed by cyclic voltammetric method,linear scanning voltammetric method and potentiostatic method.The primary contents and results are as follows.Under room temperature and atmospheric pressure,a novel Cu-C_i oxygen-evolution catalyst is generated in situ by controlling the electrolysis potential in the mild 0.1 mol/L K₂CO₃ solution?pH=10.25?with tetrakiscopper hexa-fluorophosph precursor.The composite and oxygen-evolution performance of Cu-C_i catalyst are investigated.The main catalytic components of the Cu-C_i catalyst are element Cu and O.The oxygen-evolution rate in situ is 31.67 ?mol/h and the oxygen-evolution overpotential is ?=263.8 mV at the current density of 1 mA/cm2.The Cu-C_i catalyst differs in structure and morphology from the reported Cu-based oxygen evolution catalysts.The results showed that the metal precursor affected the preparation and properties of oxygen evolution catalyst.The electrolyte plays an important role on preparation of oxygen-evolution catalyst in situ,which acts as a proton acceptor and ligand for oxygen-evolution catalyst.The electrolyte will affect the preparation and properties of oxygen evolution catalyst.An Ag-P_i oxygen-evolution catalyst is obtained in 0.1M phosphate buffer?pH=12.4?with 1mM Ag+ ion.The prepared Ag-P_i oxygen-evolution catalyst tends to be amorphous structure.The average oxygen-evolution rate is 11.1 ?mol/h and the oxygen-evolution overpotential is ?=457 mV at the current density of 1 mA/cm2.The catalytic performance of Ag-P_i oxygen-evolution catalyst is superior to the reported Ag-C_i catalyst.The ?-Ag₂WO₄,two ?-Ag₂WO₄ with different morphology,and amorphous-Ag₂WO₄ are prepared by chemical solution deposition method.The ?-Ag₂WO₄ catalyst has better oxygen-evolution properties and lower oxygen-evolution overpotential than ?-Ag₂WO₄ and amorphous-Ag₂WO₄.The average oxygen-evolution rate is 17.6 ?mol/h and the oxygen-evolution overpotential is ?=375 mV at the current density of 1 mA/cm2 in 0.1 mol/L K₂B₄O₇ electrolyte.The results showed that the Ag₂WO₄ catalysts decomposed into Ag₂O and tungsten oxide after oxygen-evolution reaction.The system temperature of the electrolyte has a great impact on the performance of oxygen evolution catalyst.Co-C_i oxygen-evolution catalysts are prepared in 0.1M NaHCO₃ with 1mM Co²⁺ ion at the temperature of 25?,50? and 70 ?.The results indicated that the phase structure of catalyst was unchanged.The particle size of the catalysts grew smaller,when the temperature of the electrolyte varies from 25? to 70?.The micro-nano structure improved the active site and reaction interface.The Co-C_i oxygen-evolution catalyst prepared under 70? has better catalytic properties.The oxygen-evolution rate increase from 7.56 ?mol/h to 29.5 ?mol/h and the oxygen-evolution overpotential decreased from 395 mV to 212 mV.Oxygen evolution in alkaline solution also plays an important role for hydrogen production.Fe-Ni Se/NF is simply and directly prepared on commercially available Ni foam without polymeric binders as an efficient and robust 3D water oxidation catalyst.When directly used as a water oxidation electrode,it demands overpotential of 233 mV and 275 mV to deliver 10 and 100 mA/cm2,respectively.It also exhibits long-time stability during the stability test in 1M KOH solution.The formed NiFeOOH at the Fe-NiSe/NF surface during OER is the actual active sites.