| With the increasing energy crisis and environmental pollution,clean energy has attracted widespread attention.Hydrogen,owing to its outstanding energy density and environmental friendliness,is considered a promising energy carrier.Among various strategies to produce hydrogen,electrochemical water splitting is increasingly attractive for its suitable manufacture safety and high product purity.As the core of electrochemical water splitting,both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)require high-activity electrocatalysts to accelerate the reaction.Therefore,exploiting non-precious metal catalysts with high activity and good stability is of great significance for the practical application of hydrogen energy.While developing new energy sources,the development of energy storage devices is equally important.Lithium-ion batteries,as new energy storage devices,have made great progress in the field of portable electronic products and electric vehicles.However,traditional batteries electrode materials are difficult to meet people's demand for energy density and power density.Therefore,it is essential to find higher performance electrode materials for lithium-ion batteries.Metal-oxogen clusters have already demonstrated great promise for electrochemical field owing to their good solubility,unique acidity and reversible redox.However,metal-oxygen clusters are easily soluble in water and organic solvents.When used as an electrocatalyst,it is difficult to achieve separation of the catalyst from the electrolyte and recycling of the catalyst;when used as an electrode material for lithium-ion batteries,metal-oxygen clusters will dissolve in electrolyte solution,which hinder the study of metal-oxygen clusters in electrochemistry.Consequently,taking full advantage of metal-oxygen clusters and solving their problems in electrochemical applications is of great significance for the research of metal-oxygen clusters in electrochemistry.In this paper,we focused on the preparation of metal-oxygen cluster-based composites and their performance in electrochemistry.From the perspectives of material design,synergetic effects and material structure,we conducted the following studies:(1)Using polyoxotungstatc as tungsten source,pyrrole as carbon source and graphenc oxide as conductive support,we synthesized polyoxotungstatc/conductivc polypyrrole/graphene(PW12-PPy/RGO,PCG)precursor by simple hydrothermal method.Then a novel tungsten carbide-based material was synthesized by carbonizing PCG directly.The NC@WxC/NRGO composite exhibits extraordinary activity towards HER in 0.5 M H2SO4 electrolyte,giving a low onset overpotential of 24 mV vs.RHE,a low Tafel slope of 58.4 mV/dec,an overpotential of 100 mV at 10 mA/cm2 and long-term stability.The excellent electrocatalytic performance of NC@WxC/NRGO toward HER could be attributed to the synergistic effects among WsC particles,NC and NRGO films.(2)Based on trinuclear metal carboxylate clusters,through the coordination between metal-oxygen clusters and organic ligands,we synthesized metal-organic frameworks(MOFs)with precise structure.And further by replacing one Fe atom in the clusters,a series of stable bimetallic MOFs were obtained.The MOFs exhibit good catalytic activity in alkaline media.Mentionablely,in the research system,all the bimetallic MOFs present the better OER performance compared with that of monometallic MOFs.The DFT calculation reveals that the introduction of the second metal atom can improve the activity of the original atom and then improve the OER performance.(3)Based on the strategy of PCG,we synthesized new precursor(PMo12-PPy/RGO)under milder conditions by taking advantage of the properties of polyoxomolybdate and the formation conditions of pyrrole.After the further treatment of ammoniation,we obtained NPC@Mo2N/NPRGO.The composite exhibits a good cycling reversibility and achieves a high capacity as a LIB anode material,which can deliver a discharge capacity of 805 mAh/g at 100 mA/g as well as an impressive rate capability. |
PDF Full Text Request