Synthesis And Application Of Polydopamine-derived Catalysts

Sustainable energy and environmental pollution have acctracted ever-increasing concerns and are main subjects of intensive research in recent years.The development of high-performance catalysts,therefore,has been the core topic in these two research areas.Focusing on efficient catalysts towards some important reactions involved in sustainable energy conversion devices and environmental pollute degradation such as oxygen reduction reaction?ORR?,Fenton reaction,and photo-degradation,this thesis develops several efficient catalysts by using polydopamine?PDA?as a multifunctional carrier capabling of adhering to eventually any solid surface and coordinating to metal ions.The chemical composition and morphology of as-prepared catalysts are characterized in detail.Their catalytic performances of synthesized catalysts are systematically evaluated.The detail contents of this paper are as follows:?1?Three Fe/N–C ORR electrocatalysts consisting of N-doped graphene with supported Fe_xN,Fe/Fe₃O₄,and Fe₃C nanoparticles?denoted as Fe_xN@N-G,Fe/Fe₃O₄@N-G,and Fe₃C@N-G,respectively?are synthesized as an efficient ORR electrocatalysts.The synthetic procedure is based on the spontaneous oxidative polymerization of dopamine in the presence of iron?III?chloride to form iron-incorporated polydopamine?PDA?layer on grapheme oxide?GO?surface,followed by thermal annealing in different atmosphere to obtain three ORR electrocatalysts with similar nanoparticle loading density and size.Systematic electrochemical evaluation indicates that Fe/Fe₃O₄@N-G exhibits the best ORR activity in alkaline media among the three materials.The nature of the active sites of the catalysts is further discussed.?2?Fe/N co-doped graphene with encapsulated Fe/Fe₃C nanoparticles?Fe/Fe₃C@Fe/N-Graphene?is synthesized as an efficient heterogeneous Fenton catalyst for degradation of organic pollutants.A precursor composed of Fe ion-incorporated PDA modified graphene oxide?Fe-PDA-GO?is prepared via a simple one-pot reaction in an aqueous solution at room temperature,followed by therm annealing in Argon?Ar?atmosphere,the precursor is converted to Fe/Fe₃C@Fe/N-Graphene.The Fe/Fe₃C@Fe/N-Graphene exhibits highly efficient catalytic activity and durability at optimal H₂O₂ concentration and catalyst dosage.?3?A modified synthetic method is further developed to synthesize Fe/N co-doped graphene with encapsulated Fe₃C nanoparticles?Fe₃C@Fe/N-G?catalyst with enhanced Photo-Fenton catalytic activity for degradation of organic pollutants.Fe³⁺/H₂O₂-Fenton-reaction-driven oxidative polymerization of dopamine on graphene oxide surface was used to synthesize the Fe-PDA-GO precursor,followed by carbonization process.Compared with the catalyst obtained in?2?,as-obtained Fe₃C@Fe/N-G catalyst exhibits higher efficiency for degradation of organic pollutants in photo-assisted Fenton reaction due to the higher loading of Fe₃C nanoparticles with smaller dimension.?4?Core–shell structured BiOCl@PDA microspheres are synthesized as an efficient photocatalyst towards the photodegradation of pollutants under simulated sunlight.It is found that the presence of dopamine in the synthetic solution greatly influence the nanostructure of the product,which exhibits hierarchical hollow microsphere stuctures formed by aggregated nanosheet with thin PDA film coated on their surface.Compared to the BiOCl synthesized in the absence of dopamine,as-prepared BiOCl@PDA exhibits higher performance for photodegradation of pollutants due to higher specific surface areas and more efficient visible light absorption.