Synthesis And Electrocatalytic Performance Of Transition Metal Ni/Co/Fe-based Nanomaterials

Oxygen evolution reaction?OER?plays a crucial role in electrochemical energy conversion devices,including fuel cells,metal-air cells and water electrolysis devices.However,the industrial application of OER is greatly affected by its sluggish intrinsic kinetics.Therefore,developing OER electrocatalysts which are economically,active,durable and effective is still a challenge.In addition,the monitoring of glucose concentration of blood is closely related to the health of the public.Excessive glucose concentration will increase the possibility of getting diabetes with a series of accompanying complications.Thus,the research on glucose sensor is of great significance.Developing non-enzymatic glucose sensor with low cost,high efficiency and good stability catch the attention of worldwide researchers.Transition metal composites are widely used in considerable fields due to the low cost to prepare,facile process to synthesize and flexible structure to modify.Transition metal composites?based on Ni,Co and Fe?are environment-friendly,stable and active,which can be applied in the research on OER and glucose sensor.Herein,in this thesis,a series of transition metal materials with unique nanostructures have been designed and synthesized and the relationship between microstructures and electrochemical properties for the materials in OER and glucose sensors have been systematically explored.The main contents and results are as follows:1.Coral-like Co_0.875Fe_0.125OOH nano-net array was prepared on carbon cloth by a hydrothermal method.The optimal metal ratio of Co and Fe is 7:1.When Co_0.875Fe_0.125OOH/CC is used as OER catalyst in 1.0 M KOH,the overpotential is 300mV at thecurrent density of 20 mA cm^-2,the Tafel slope is 83 mV dec^-1,and the stability is still robust after 50 h continual measurement.It can be concluded that the introduction of cobalt ions significantly enhances the electrocatalytic activity of FeOOH based materials.2.By a combined process of hydrothermal and phosphoridation methods,the Ni₁V₁P nanosheets self-assembled microspheres were directly grown on the nickel foam.This study aims at exploring the effects of different metal ratios on the morphology and electrochemical properties and verifying that the optimal ratio of Ni and V is 1:1.As an OER catalyst,due to the unique 3D nanosheet-based microsphere and good conductivity,Ni₁V₁P NSs/NF only requires an overpotential of 250 mV and290 mV when the current density reaches 50 mA cm^-2 and 100 mA cm^-2,respectively.And the materials persist a long-term electrochemical stability of 15 h in alkaline solution.3.A novel CoFeB nanosheet array with partial-amorphous properties was directly grown on the nickel foam by an electroless plating method.This research investigates the effects of different reacting times on microstructures and electrochemical properties of the materials.As OER catalysts,CoFeB-5-30/NF has a specific partial-amorphous feature and highly ordered nanosheet structure,which can increase the active surface areas,provide more active sites,and facilitate the release of O₂ bubbles formed when reacting.Besides,the synergistic effect of Co and Fe promotes the electron transportation of the materials.In alkaline solution,the overpotential is only 260 mV when the current density achieves 20 mA cm^-2,and the slope of Tafel is 38 mV dec^-1.After continual 60 h reaction at the current density of 20,50 and 100 mA cm^-2,respectively,the materials still exhibit high activity and robust stability.4.Porous NiTe₂ nanosheet arrays grown on carbon cloth by a hydrothermal method can be utilized as a high catalytic active electrode for the electrochemical oxidation of glucose under alkaline conditions.When used as a highly efficient electrochemical sensor for non-enzymatic glucose detection,the material has a response time less than 5 s,a linear range from 0.001 to 6 mM,a detection limit as low as 0.12?M?S/N=3?,and a high sensitivity(up to 5146 mA mM^-1 cm^-2).In addition,the NiTe₂ nanosheet array can be also prepared for the effective detection of glucose in real human serum and fruit juice.5.Co-MOF nanosheet arrays were grown on nickel foam by a hydrothermal reaction of aqueous Co²⁺and terephthalic acid.This Co-MOF/NF can be used as an excellent sensor for non-enzymatic glucose detection under alkaline conditions.Co-MOF/NF has a fast ampere response of less than 5 s,as well as a high sensitivity of 10886?AmM^-1 cm^-2 and a low detection limit of 1.3 nM?S/N=3?.The material has a high selectivity and reproducibility of catalytic activity for the electrooxidation of glucose and has been successfully applied to the analysis of practical sample.