Design And Preparation Of Bimetallic Cobalt Ruthenium Catalysts And Their Performances For Electrocatalytic Water Splitting

With the sharp reduction of fossil energy and the increasing environmental pollution,the demand for clean and sustainable alternative energy sources has become very urgent.Electrochemical water splitting includes two half reactions,named hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?,but the efficiencies of both OER and HER are usually limited in the electrochemical water splitting.Therefore,efficient catalysts are needed to accelerate the reaction speed to further reduce energy consumption.Until now,it is recognized that the best catalyst for HER is the noble metal Pt,and the best catalysts for OER are IrO₂ and RuO₂.However,the large-scale practical applications of them are limited due to the scarcity and high cost of precious metals.In this dissertation,a series of ruthenium–cobalt-based composite catalyst were designed and prepared,to ensure the catalytic activity of the catalysts and reduce the operating costs.The main research contents are as follows:1.Polyhedron-structured metal-metal oxide@N-doped carbon?RuO₂-Co₃O₄/CoRu@NC?with different Co/Ru ratios was prepared by using porous metal-organic framework?MOF?as template through successive ion exchange-high temperature pyrolysis and surface oxidation processes.The electrocatalytic water splitting performance was tested in 0.5M H₂SO₄ solution.The prepared RuO₂/Co₃O₄-RuCo@NC-1.95 was highly active for catalyzing both OER and HER with low overpotentials of 247 m V and 141 mV at 10 mA cm^-2,respectively.Furthermore,when employed as a bifunctional electrocatalyst for acidic overall watersplitting,the RuO₂/Co₃O₄-RuCo@NC achieved a current density of 10 mA cm^-2at only 1.66 V with good long-term stability.In light of the above experimental results,we infer that the origin of the excellent OER performance of our RuO₂/Co₃O₄-RuCo@NC could be attributed to their unique structure,where the reserved carbon framework as the protecting skeleton not only prevented metal components from aggregation and corrosion in acidic medium,but also served as active site regulator to promote adsorption of intermediates and optimize the binding energy between the reaction intermediate through redistributing the charge and spin density.2.Using a similar method to the previous chapter,only changing the solvent in the MOF template synthesis process,by replacement of methanol with water,a leaf-like structured metal-metal oxide@N-doped carbon?RuO₂-Co₃O₄/CoRu@NC?with different Co/Ru ratios was prepared.The morphology,structure,and composition of the samples were analyzed by means of X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,high-resolution TEM?HRTEM?,X-ray photoelectron spectroscopy?XPS?and other characterization methods.The electrocatalytic water splitting performance was tested in 1M KOH solution.The oxygen overpotentials at a current density of 10 mA cm^-22 of RuO₂-Co₃O₄/CoRu@NC-4.55 was 168 mV.This value is favorably compared to most of the catalysts previously reported.3.By using MOF to modify the surface structure of Co?CO₃?_0.5?OH?·0.11H₂O/Ti nanowire array.RuO₂-Co₃O₄/Ti with different Co/Ru ratios was prepared by ion exchange-thermal calcination method.The morphology,structure,and composition of the samples were analyzed by means of XRD,SEM,TEM,HRTEM,XPS and other characterization methods.The electrocatalytic water splitting performance was tested in 1 M KOH solution.RuO₂-Co₃O₄/Ti-24 can deliver a current density of 10 mA cm^-2at an overpotential of 230 mV,along with a Tafel slope 128mV dec^-1,which has good stability...