Electrocatalytic Performance Regulation Of Transition Metal Polyporphyrin-Derived Hybrid Materials

The sustainable development of human society has been significantly hindered by increasingly serious problems of environmental issues and climate change due to the combustion of traditional fossil fuels and the population growth.Electrochemical energy conversion and storage technologies such as fuel cells,metal-air batteries,and water splitting cells have attracted intensive attention due to their advantages such as high efficiency,environmental friendliness,and sustainability.Among them,zinc-air batteries and water splitting technologies involve oxygen reduction reactions(ORR),oxygen evolution reactions(OER)and hydrogen evolution reactions(HER).At present,the state-of-the-art electrocatalysts are all based on precious metals such as platinum,iridium and ruthenium.However,the disadvantages of these noble-metal catalysts such as low reserves,high cost and poor stability seriously hamper the large-scale commercialization of Zn-air batteries and water splitting.Therefore,developing low cost,highly active and stable non-noble-metal bifunctional catalysts is of great necessity but remains challenging.In this dissertation,three novel transition metal-based hybrid materials derived from transition metal-coordinated polyporphyrin are designed and prepared,and used as nonnoble-metal electrocatalysts for ORR,OER and HER.The morphological and structural properties of the as-prepared hybrid materials are characterized by using SEM,TEM,HAADF-STEM,XRD,XPS and Raman spectrum techniques.The electrocatalytic performance of the as-obtained catalysts are studied by electrochemical methods such as CV,LSV,RED,RRED,i-t and ADT.Many valuable results are obtained and summarized as follows.Firstly,novel Fe-Co alloy nanoparticles-embedded N-doped carbon coated carbon nanotubes hybrids,named CNTs@(Fe,Co)PP-T(where T represents the pyrolysis temperature),are successfully prepared by pyrolyzing the Fe/Co polyporphyrin-encapsulated carboxylic carbon nanotubes,followed by the acid leaching procedure.The optimized CNTs@(Fe,Co)PP-700 catalyst shows remarkable electrocatalytic activity and good stability for both ORR and OER.The assembled zinc-air battery using CNTs@(Fe,Co)PP-700 as the air electrode displays high peak power density,low charging-discharging voltage gap and excellent charge-discharge cycling stability,superior to the noble Pt/C+Ru O2 based Zn-air battery.Secondly,a novel nickel foam(NF)-supported spherical core-shell Fepoly(tetraphenylporphyrin)/Ni-poly(tetraphenylporphyrin)microparticles is obtained by a facile liquid-phase synthesis method.The as-prepared Fe TPP@Ni TPP/NF possesses outstanding electrocatalytic performance for both OER and HER in alkaline media.Using Fe PP@Ni PP/NF as cathode and anode,the assembled water electrolyzer shows lower cell voltage for overall water splitting than that respectively using Pt/C and RuO2 as cathode and anode.Thirdly,silica template-assisted and mesoporous silica-protection synthetic strategies are used to produce a hierarchically porous bimetallic Fe/Co-Nx-C single-atom electrocatalyst.The catalyst shows outstanding electrocatalytic activity and excellent durability for ORR,even superior the commercial Pt/C catalyst.The work provides a new synthetic strategy to fabricate highly active and stable single-atom catalysts for zinc-air batteries.