Study On Design And Properties Of Transition-metal-containing Polyoxometalate-based Complexes

With the development of science and technology,energy and environmental issues have always been the shackles of people.In order to create a resource-saving and environment-friendly society,new energy materials have become the focus of many researchers.Nowadays,in the era of Internet of things and artificial intelligence,miniaturized,portable and wearable electronic products（such as mobile phones,tablets,electronic bracelets and Bluetooth headsets）and self-powered sensors（such as electronic skin）have become an integral part of our daily life.However,these electronic products are faced with the problem of insufficient power supply and poor endurance,which has always attracted people’s attention.Triboelectric Nanogenerator（TENG）can effectively collect the mechanical energy of human movement and convert it into electrical energy.Not only that,it has good flexibility and biocompatibility,and can be used as a portable and wearable power supply system.In the past decades,polyoxometalates（POMs）based materials have been studied and proved to be energy materials with high performance and high stability.In this paper,polyoxometalate based organic-inorganic hybrid materials were first applied to TENG as friction layer,and it was found that they had high output performance and stability.1.With the rapid development of TENG,it is urgent to develop novel friction materials to expand the conventional materials in triboelectric series to meet the diverse requirements of far-ranging applications.In this work,twoα-Keggin-type POMs-based metal-organic hybrid compounds were synthesized through the finetuning of the reactants under the same reaction conditions,including one discrete ionic structure[Zn（4,4′-bpy）₂（H₂O）₄][4,4′-H₂bpy]₂[Zn W₁₂O₄₀]·4H₂O（1）and one one-dimensional infinite chain structure{[Cu（H₂TPT）₂（H₂O）₂][Zn W₁₂O₄₀]}_n（2）.They were first used as triboelectric layers,together with polyvinylidene fluoride（PVDF）as the opposite layer to fabricate TENGs.The results displayed that the TENG based on the discrete hybrid with higher permittivity displayed superior output performance of 395 V and 34.8μA and demonstrated good stability during cyclic measurement of over 50,000 cycles.2.In order to improve the output performance of TENG,twoα-Keggin type POMs,[Zn ^IIW₁₂O₄₀]^6-({Zn W₁₂})and[Co ^IIW₁₂O₄₀]^6-({Co W₁₂})were self-assembled with metal ions and organic ligands to form inorganic organic hybrid materials as friction layers.By comparing the output performance of TENG assembled by POM based materials with different hetero elements,the high output performance TENG was obtained.Here,three kinds of Cu²⁺modifiedα-Keggin POMs based inorganic-organic hybrid materials were synthesized byhydrothermalmethod:{[Cu（4,4’-bpy）（HNMe₂）₂]₂[H₂Zn W₁₂O₄₀]}_n（3）,[Cu（2,2’-bpy）（4,4’-Hbpy）（H₂O）]₂[Co ^IIW₁₂O₄₀]（4）and{[Cu₂（2,2’-bpy）₂（4,4’-bpy）（H₂O）][Cu（2,2’-bpy）₂][Co ^IIW₁₂O₄₀]}_n（5）.By comparing 3-TENG with 4-TENG,it is found that the output performance of 4-TENG(I_SCand V_Oare 78.3μA and386 V)is much higher than that of 3-TENG.In addition,we found that 4-TENG>3-TENG>Co W₁₂-TENG>Zn W₁₂-TENG,which proved that POM based inorganic-organic hybrid materials containing hetero element Co were selected to be used in TENG and had a broad application prospect.3.In order to obtain high performance,high stability,flexibility and biocompatibility TENG,inorganic-organic hybrid materials were prepared by modifying inorganic and organic building units with transition metal ions.Two kinds of inorganic-organic hybrid crystal materials[Zn（2,2’-bpy）₂（H₂O）]₂（4,4’-bpy）₂[H₂Co ^IIW₁₂O₄₀]（6）and[Zn（2,2’-bpy）（4,4’-bpy）（H₂O）][Zn（2,2’-bpy）₃][H₂Co ^IIW₁₂O₄₀]·5H₂O（7）modified by Zn²⁺ions were obtained by hydrothermal method in one reactor.Here,we found that the output properties of 6,7-TENG with I_SCand V_Oof 105.3μA and 532 V are much higher than those of TENG(2,2’-bpy-TENG,4,4’-bpy-TENG and Co W₁₂-TENG),which are the building materials of inorganic and organic parts of the material,thus highlighting the advantages of this inorganic-organic hybrid material.