Preparation Of Iron Group-based Transition Metal Electrocatalysts And Their Performances For Oxygen Evolution Reaction

Hydrogen is widely concerned because of its zero pollution of combustion products,high combustion energy and reproducibility,and is expected to meet the growing energy demand of the world.Hydrogen has a wide range of sources and various preparation methods.The electrocatalytic water splitting is a promising method,which has the advantages of zero pollution and high purity of hydrogen production,The process of water electrolysis consists of two half reactions:the hydrogen evolution reaction?HER?at the cathode and the oxygen evolution reaction?OER?at the anode.The OER reaction is a rate-limiting step in the above-mentioned reaction system,needing to undergo a four-electron transfer process,where the O-H bond is broken and the O-O bond is generated,This results in the OER reaction bearing a much larger overpotential than the HER.At present,ruthenium-iridium-based electrocatalysts can catalyze OER more effectively,but the high price limits their wide application.Therefore,it is urgent to develop high-efficiency electrocatalysts base on earth-abundant elements for electrocatalytic water splitting.This dissertation mainly focuse on the design and synthesis of the electrocatalyst for catalyzing the oxygen evolution reation based on the iron group transition metal elements?cobalt,nickel and iron?,in order to achieve a cheap and efficient electrochemical water decomposition process.The main content are as follows:1.Using cobalt-nickel metal nitrate as raw material,the benzoate intercalated nickel-cobalt hydroxide nanobelts with different Co/Ni ratios were synthesized by one-step hydrothermal method.By regulating different reaction conditions,the optimal benzoate intercalated ultra-thin nickel-cobalt hydroxide nanobelts were obtained.The composition,morphology,structure and OER performance of electrocatalytic system were systematically studied.Co_xNi_1-x?OH??BzO?·H₂O nanobelts have p-p junctions and good energy level matching,endowing them with excellent OER performance in alkaline environment.In particular,the optimal sample Co_0.8Ni_0.2?OH??BzO?·H₂O showed an earlier initial potential?1.50 V vs RHE?and a smaller overpotential(?₁₀:319mV).2.Using magnesium oxide as a template and a reaction source,a nickel-iron hydroxide with a nanosheet micro sphere morphology was synthesized through a hydrolysis-coprecipitation process.Their composition,structure and morphology were characterized in detail by a series of measurement tachniques.Bimetallic nickel-iron hydroxide shows better electrocatalytic oxygen evolution reaction performance in alkaline medium than that of individual nickel hydroxide and iron hydroxide.Its overpotential at a current density of 10 mA cm^-2 is only 260 mV.This excellent performance is related to its bimetallic synergy and unique nanosheet structure.3.Using cobalt nitrate as the cobalt source,a cobalt hydroxide precursor intercalated with salicylate was synthesized by one-step hydrothermal method.By calcining the synthesized precursor under N₂ atmosphere,the cobalt oxide?CoO?electrocatalyst was synthesized.The optimal conditions of cobalt oxide nanorods were obtained by optimizing the relevant reaction condition.By testing its OER performance in 1 M KOH solution,cobalt oxide at 400?shows better electrocatalytic performance.Its onset potential is 1.47 V vs RHE,and the overpotential at a current density of 10 mA cm^-2 is only 276 mV.