Synthesis Of Oxygen Evolution Reaction Catalyst For Water Splitting Via Deep Eutectic Solvent-Based Lonic Liquid And Its Electrocatalytic Performance

There is an over-reliance between the development of our society and the usage of fossil fuel.As the society develops at a higher speed,the amount of need and usage to fossil fuel is also rising,which brings two serious issues to us,energy shortage and environmental pollution This severe situation pushes us to find more efficient and clean energy substitutes.Hydrogen,produced by water splitting,is an ideal new type of energy due to its high efficiency and other characteristics like renewable and pollution-free.The water splitting process consists of two electrode half-reactions,oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).Compared to HER,OER requires a much larger o verpotential,and thus consumes more electrical energy.Therefore,how to produce an efficient catalyst for OER to reduce its overpotential has attracted lots of researchers'interests in the water electrolysis field.For now,the Ru-and Ir-based noble metal catalysts gain the best capability,but their short storage and high cost set up limitations from industrial application.Hence,the key to realize the industrial application of electro-catalysis water splitting is to develop electrocatalyst that is easily-compound,low-cost and efficiently-performed.Deep eutectic solvent(DES),as a new type of ionic liquid,shares lots of characteristics with ionic liquid(IL),and it is cheap and environment-friendly,has a promising application prospect in the direction of nano-particle synthesis.This thesis is devoted to state the production of electrocatalyst with a DES compound strategy,which means using the DES's characteristics to simplify the compound procedures and improve catalytic capability,and to investigate the relations between different factors like composition and morphology of electrocatalyst and its capability.The main contents of this research are as follow.(1)In this work,a new class of pre-electrocatalyst,2D[Co(NH3)4CI3]Cl nanosheets,was developed by a DES self-species method,corresponding to an all-in-one strategy.The 2D[Co(NH3)4CO3]Cl pre-electrocatalyst can transform to CoOOH with robust electrocatalytic performance after activation process.The CoCl2·6H2O-urea based DES can not only works as the solvent,but also serves as the all reactants and template for the construction of the catalysts.After activation process,[Co(NH3)4CO3]Cl nanosheets can be transformed to amorphous CoOOH.As a result,the catalyst shows an excellent electrocatalytic activity,which requires a low overpotential of 291 mV to reach 10 mA cm-2 and possesses a low Tafel slope of 65 mV dec-1.Moreover,the long-term stability results indicate its good durability for OER.Owing to the facile synthetic method meeting the requirement of atom economy,the present all-in-one DES strategy thus provides more opportunities for the rational design of advanced OER catalysts through sustainable and green way.(2)In order to improve the oxygen evolution reaction performance of Fe-based electrocatalysts,we rationally designed porous nanosheets of Fe7S8/Fe2O3 composite with abundant oxygen vacancy through a DES-mediated strategy.The choline chloride(ChCl)-glycerol DES serves as a morphology-control environment to form a 2D nanostructure of Fe7Sg/Fe2O3 composite,and the annealing process in N2 atmosphere at 400? results in the formation of abundant oxygen vacancy.The as-prepared Fe7Sg/Fe2O3 with oxygen vacancy boosted the electrocatalytic activity towards OER,which requires only a low overpotential of 229 mV to reach a current density of 10 mA cm-2 and processes a low Tafel slope of 49 mV dec-1 in 1 M KOH.Moreover,the long-term stability results indicate its good durability for OER.