| Hydrogen is a green and renewable energy with the advantages of high energy density and pollution-free of combustion products,so hydrogen energy is an ideal alternative substitute for fossil fuels.Thereinto,electrolytic hydrogen evolution reaction is a feasible technology to achieve large-scale hydrogen production.Meanwhile,supercapacitor,as a kind of energy storage device with high power density,high energy density,long cycle life,environmental friendliness and high safety.And the electrode material is a key factor,which determine the hydrogen production efficiency of electrolytic hydrogen evolution reaction and the construction of high performance supercapacitors.The most conventional and excellent electrode materials are noble metal materials and their composites,but the high-price and rareness considerably restrict their extensive applications.Therefore,one of the pivotal point to be solved urgently in the field of energy is designing and preparing new high-performance noble-metal-free electrode materials.Polyoxometalate?POM?,a kind of nano-scale multinuclear molecular cluster based on early-transition elements.POMs have structural diversity,modifiability,and the ability of multi-electron transfer without the structural changes,which is widely utilized in electrochemical field.POM-based coordinated polymers with abundant composition and diverse structure,which could efficaciously design and regulate the classification and numbers of metals at molecular or even atomic levels by modificating POMs with metal ions and organic ligands.Composite material with excellent electrochemical properties,which can be prepared by using POM-based coordinated polymers as precursor and in-situ self-assembly-thermal conversion technology.Accordingly,six POM-based coordinated polymers with novel structures were designed and fabricated and considered as precursors reacting with thiourea/graphene to synthesize six composite material,and study the electrolytic hydrogen evolution supercapacitors performance.The main contents of the study are as follows:1. Two new silicomolybdate acid metal-organic polymers crystal materials have been firstly designed and synthesized by utilizing Keggin silicomolybdate acid as POM source,cobalt acetate/nickel nitrate as metal source,Htrz as organic ligand:?trz=1,2,4-triazole=C2H2N3?The crystal structures of 1 and 2 are isostructural,and exhibit three-dimensional?3D?supermolecular structure via numerous hydrogen bond interactions between{Co2?trz?3·6H2O}/{Ni2?trz?3·6H2O}binuclear metal fragment and[Si Mo12O40]4-(Si Mo12)Keggin cluster.And they can be expected to be a great‘preassembly platform'for directing the formation of bimetallic sources with flower-like structure.The experimental results of electrocatalytic hydrogen evolution reaction show that50%Co S2-Mo S2and 50%Ni3S2-Mo S2composites display a low overpotential of 222and 224 m V at 10 m A·cm-2,and a small Tafel slope of 64.2 and 65.7 m V·dec-1in 0.5M H2SO4solution.2. A new germanomolybdate acid metal-organic polymer crystal material has been designed and synthesized by utilizing germanic oxide and sodium molybdate as POM source,nickel nitrate as metal source,Htrz as organic ligand:?trz=1,2,4-triazole=C2H2N3?The three-dimensional?3D?supermolecular structure 3 is achieved by numerous hydrogen bond interactions between{Ni2?trz?3·6H2O}binuclear metal fragment and[Ge Mo12O40]4-(Ge Mo12)Keggin cluster.And Ni3S2-Mo S2-r GO-200-24-2?abbreviate to Ni-Mo-S-r GO-200-24-2?is formed by the mixture of 3 and oxidized graphene?GO?under thiourea.Ni-Mo-S-r GO-200-24-2 display ultra-low onset overpotential??15 m V?,low overpotential of 118 m V at 10 m A·cm-2,and excellent stability(at current density 10 m A·cm-2for 20h)in 1.0 M KOH solution.3. A new germanomolybdate acid metal-organic polymer crystal material has been designed and synthesized by utilizing germanic oxide and sodium molybdate as POM source,cobalt acetate as metal source,Htrz as organic ligand:?trz=1,2,4-triazole=C2H2N3?The three-dimensional?3D?supermolecular structure 4 is achieved by numerous hydrogen bond interactions between binuclear cobalt fragment and Keggin clusters.The Co S2-Mo S2in the form of vertically interconnected nano-arrays with multiple interfaces are firstly grown in-situ on carbon cloth without adding additional binder by utilizing 4 as‘preassembly platform',and directly used as working electrode.The as-synthesized Co S2-Mo S2-CC-30h exhibits preeminent electrocatalytic hydrogen evolution reaction performance(65 m V for 10 m A·cm-2vs RHE in 0.5 M H2SO4electrolyte,87 m V for 10 m A·cm-2vs RHE in 1.0 M KOH electrolyte),and long-term stability.4. Two novel POM-incorporated metallacalix[6]arene compounds have been firstly designed and synthesized by utilizing Keggin silicotungstate acid/silicomolybdate acid as POM source,silver nitrate as metal source,Htrz as organic ligand:?trz=1,2,4-triazole=C2H2N3?The POM-incorporated metallacalix[6]arene 5 and 6 are isostructural,and 1D Ag-POM chain are incorporated into top and down windows of the double metallacalix[6]arene of the metallacalixarene framework to form unique 3D POM sandwiched metallacalix[6]arene framework.The specific capacitance and capacitance retention of 5-based electrode is 155.0 F g-1at 0.5 A g-1and 78.5%after1000 cycles.For the sake of further effectively enhancing the supercapacitor performance of 5,5-n Graphene Oxide?GO?composite materials have been prepared by ultrasonic,defined as 5-n GO?“n”=5%,10%,15%and 20%,respectively?.Thanks to the synergetic effects of GO and POM-incorporated metallacalix[6]arenes,5-15%GO-based electrode exhibits the highest specific capacitance up to 230.2 F g-1(current density equal to 0.5 A g-1),encellent capacitance retention?92.7%after 1000cycles?,low overpotential(212 m V for 10 m A·cm-2vs RHE)and small Tafel slope(79.1 m V·dec-1)in 0.5 M H2SO4electrolyte. |
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