Preparation And Electrochemical Properties Of Bimetal Composite Micro-nano Materials

Compared with non-nano materials,bimetal composite micro-nano materials have many characteristics,such as colorful microstructures,high specific surface areas,good electrical conductivity,and characteristic synergistic interactions,etc.It can be used as electrochemical energy storage material,electrocatalytic material,photocatalytic material and electroanalytical detection material,etc.It is widely used in lithium ion batteries,electroanalytic detection technology,electrocatalytic water splitting,enzyme-free glucose sensors,and other emerging fields.Therefore,it is of great significance to use simple,controllable and green methods to prepare all kinds of low-cost bimetal composite micro-nano materials.In this thesis,several bimetal composite micro-nano materials were rapidly prepared by electrochemical method,successive ionic layer adsorption and reaction method and photochemical reduction method.Scanning electron microscope,transmission electron microscope,X-ray powder diffractometer and X-ray photoelectron spectroscopy were used to characterize the prepared bimetal composite micro-nano materials,which were applied to non-enzymatic glucose detection and electrocatalytic water splitting.The main contents are as follows:1.Herein,a novel thin film of layered micro-chips of compact rice grain-like Cu/Ni?OH?₂ nanocomposites has been fabricated via a new electrochemical route.It is achieved in a short time?1500 s?by applying square wave potential pulses?between 0.2 V and-1.7 V vs.SMSE?to treat a smooth Cu-Ni-Zn disk electrode in a 2 mol dm^-3 NaOH solution.The oxidation products of Zn?OH?₄^2-,CuOOH and NiOOH at 0.2 V from the Cu-Ni-Zn electrode surface are dissolved in the solution and reduced to nanocomposites of Cu nanowires and Ni?OH?₂ nanosheets at-1.7 V,respectively.The presence of Zn in the alloy and its dissolution from the alloy surface play the key role for the formation of the layered micro-chips.The layered micro-chips of rice grain-like Cu/Ni?OH?₂ nanocomposites enlarge the active surface area of the thin film,which enhances the electro-oxidation of glucose and the performance in sensing glucose.The prepared thin film of micro-chips of Cu/Ni?OH?₂ nanocomposites can serve as an advanced non-enzymatic glucose sensor.It has these merits of low detection limit(0.37?mol dm^-3),high sensitivity(3624(?A mmol dm^-3)^-1 cm^-2),wide linear range(2?mol dm^-3?6.1 mmol dm^-3),long-term stability?five-week storage?,and accurate analysis of glucose in human blood.2.Nickel foam?NF?surface micro-nano rough treatment and composite modification for electrocatalytic water splitting.NF is a non-noble metal with three-dimensional network structure,which is extensively utilized in electrocatalytic thanks to its preeminent electrical conductibility as well as poriness.In this paper,the square-wave potential method?0 V?-1.8 V,200 Hz,500 s?was used to roughen the surface of NF to obtain a rough surface at the micro-nano scale;and then processed by cyclic voltammetry to obtain the hydrogen evolution electrode of NF/Ni?OH?₂composite with micro-nano structure;continued to modify the appropriate amount of Fe with successive ionic layer adsorption and reaction method?SILAR?to obtain the oxygen evolution electrode of NF/Ni?OH?₂/Fe?OH?₂composite with micro-nano structure.After the above surface treatment and modification,the NF can efficiently decompose water by electrocatalysis.In the 1 mol dm^-3 KOH solution,the two-electrode electrolytic cell is formed by using the prepared electrode as an anode and a cathode,respectively.It exhibits excellent water electrolysis performance.When the current density reaches 10 mA cm^-2,only a voltage of 1.63V is required.The 10-hour electrolysis test shows that the electrolytic cell has strong stability when used to split water.3.Nano-metallic oxides support trace amounts of Pt for electrocatalytic decomposition of hydrogen from water.Photochemical method is used to reduce the H₂PtCl₆ adsorbed on the nano oxide?TiO₂ and WO₃?support to obtain a nanocomposite electrocatalyst.We explored the effect of different Pt loadings on the catalyst's hydrogen evolution performance and compared it with the hydrogen evolution effect of commercial 20 wt%Pt/C.Among them,the hydrogen evolution current density of WO₃-0.25?mol Pt based on geometric area and platinum mass are both better than commercial 20 wt%Pt/C.The fabricated WO₃-0.25?mol Pt electrocatalyst shows an overpotential of 29 mV at 10 m A cm^-2 for HER in 0.5 mol dm^-3 H₂SO₄.The preparation method is simple and fast,and without adding any reducing agent and protector.