Preparation And Electrocatalytic Performance Study Of Bimetallic Nanocomposites For Oxygen Reduction And Hydrogen Evolution As Well As Oxygen Evolution Reactions

Recently,the global energy crisis caused by the heavy reliance of fossil fuels and anthropogenic climate change have provoked the urgent need to search alternative sources of carbon-neutral,clean and renewable energy.Hydrogen,which possesses high mass energy density and zero pollution,has been widely considered as an ideal and renewable energy.Electrochemical water splitting is one of the most effective technologies to generate high-purity hydrogen.Meanwhile,proton exchange membrane fuel cell?PEMFC?has become one of the most promising energy conversion devices because of its mild working conditions,high energy conversion efficiency,and environmental friendliness.However,both the oxygen evolution and hydrogen evolution reactions at the cathode and anode of water electrolysis,as well as the oxygen reduction reaction at the cathode of proton exchange membrane fuel cell,need efficient and durable catalysts to reduce the high electrochemical overpotentials to facilitate the sluggish reaction kinetics.In this work,a series of bimetallic nanocomposites have been synthesized by simple green experimental methods.The relationship between the morphology,structure,properties and the catalytic activity of the samples was analyzed by various characterization means.The main contents of this thesis include the following three parts:?1?A series of AuPt alloyed nanomaterials with peptide Z1 as ligand were prepared by a facile wet chemical method,and the AuPt alloys were employed as catalysts for both oxygen reduction reaction?ORR?and hydrogen evolution reaction?HER?.The morphology of AuPt alloyed nanoparticles was regulated by changing the Au-to-Pt ratio,where the Au₃₃Pt₆₇ sample showed peanut shape,and the other samples possessed granular structure.Among the series,Au₃₃Pt₆₇ showed the best bifunctional electrocatalytic performance.Au₃₃Pt₆₇ exhibited superior ORR and comparable HER activities to commercial Pt/C catalyst.Furthermore,Au₃₃Pt₆₇showed higher long-term stability than that of Pt/C for both ORR and HER.?2?A series of PdRu alloyed nanoparticles encapsulated in porous carbon nanosheets derived from MOFs were fabricated by in-situ reduction and employed as bifunctional electrocatalysts for both ORR and HER.The composition and structure of the as-formed catalysts were fine-tuned by changing the ratio of Pd-to-Ru.The PdRu alloyed nanoparticles were mainly encapsulated in the mesopores of carbon nanosheets.Among a series of samples tested,Pd₅₀Ru₅₀/CNs showed comparable ORR activity to that of commercial Pd/C catalyst,but its HER activity was better than that of Pd/C in both acidic and alkaline solutions.Notably,the long-term stability of ORR and HER of Pd₅₀Ru₅₀/CNs was also higher than that of commercial Pd/C.?3?A facile wet chemical method was employed to create Ni@Ru core-shell nanoparticles on flower-like carbon nanosheets for HER at all pH values,OER and overall water splitting?OWS?in alkaline media.The synthesized samples had a three-dimensional flower shape on the whole,including two-dimensional carbon nanosheets as the substrate,while the Ni@Ru core-shell particles are located on the surface of the carbon nanomaterials.Among the as-synthesized samples,Ni@Ru/CNS-10%exhibited the best HER and OER properties in alkaline media,and superior long-term durability to Pt/C and RuO₂ for HER and OER,respectively.It also demonstrated outperformed capability than both Pt/C and RuO₂ in OWS test.In addition,in acidic and neutral media,Ni@Ru/CNS-10%showed excellent catalytic activity and stability of HER as well.