Electrochemical Construction Of Micro-nano Structures On Au Alloy Surface And Its Electroanalytical Applications

Micro-nanostructured metal electrodes are widely used in the field of electrochemistry due to their good conductivity,large electrochemical activity area and high electrocatalytic activity.Bimetallic micro-nanomaterials have better electrochemical performance than single metals because of the adjustable chemical compositions and structures and the synergistic effects between two different metals.Most of the micro-nanostructured bimetallic materials are synthesized using a bottom-up approach,such as molecular beam method,chemical/electrochemical reduction method,hydrothermal method,etc.The preparation process is complex and time-consuming.When they are empolyed as an active catalytic material to modify the substrate electrode,tedious and time-consuming modification steps are required and the repeatability of experiments is usually poor.Here,a top-down approach is used to fabricate micro-nanostructured bimetal materials.Starting from Au alloy?AuCu,AuPd,AuAg?,several simple electrochemical methods,including electrochemical cyclic voltammetry,potentiostatic oxidation,double potential step method and square wave pulse method,were used to directly construct micro-nanostructures on the surface of these Au alloys.As-prepared electrodes are seamless integrated and self-supporting,and can be used for the electrochemical detection of hydrazine hydrate,hydrogen peroxide and ascorbic acid.These micro-nanostructured bimetal materials show better electrochemical performance than single metal nanomaterials.Compared with the commonly used chemically modified electrode method,the method used in the paper has the advantages of simple,rapid preparation and good repeatability.The main work of this paper includes:?1?A micro-nanostructure porous film?MNPF-AuCu?electrode was prepared by cyclic voltammetry in KCl electrolyte on the surface of smooth Au₂₅Cu₇₅?at.%?alloy.It was used as electrochemical sensor to detect N₂H₄ in alkaline condition.The preparation time,potential range and electrolyte concentration are optimized.The surface morphology,composition and structure of MNPF-AuCu were characterized by SEM,EDS,XPS and XRD.MNPF-AuCu has high electrocatalytic activity for N₂H₄ oxidation in NaOH solution.As a N₂H₄ electrochemical sensor,MNPF-AuCu electrode has high sensitivity(2660?A cm^-2 mM^-1 and1562?A cm^-2 mM^-1),wide linear range?4?M?6.104 mM and 6.104?13.104 mM?,good reproducibility,repeatability and long-term stability?up to 7 months?,and has been successfully used for the detection of N₂H₄ in river water and tap water with satisfactory recovery.?2?A strip nanoporous membrane?RNPF-AuPd?electrode was prepared by potentiostatic anodizing in HCl electrolyte on the surface of a smooth Au₈₀Pd₂₀?at.%?alloy.A dual-function electrochemical sensor for the detection of N₂H₄ and H₂O₂ in alkaline condition was constructed.The anode potential,anodizing time and electrolyte concentration are optimized.The surface morphology,composition and structure of RNPF-AuPd were characterized by SEM,EDS,XPS and XRD.The synergistic effect between Au and Pd enhanced the electrocatalytic performance of RNPF-AuPd electrode for N₂H₄ oxidation and H₂O₂reduction in NaOH solution.The sensor has good repeatability,reproducibility and long-term stability?8 weeks?.The sensitivity of the sensor to N₂H₄ is 4583?A cm^-2 mM^-1,the linear detection range is 4?M?10.104 mM;the sensitivity to H₂O₂ is 1352?A cm^-2 mM^-1,the linear detection range is 20?M?16.104 mM.?3?A network-like nanoporous membrane?Net-AuPd?electrode was prepared in KCl electrolyte on the surface of a smooth Au₃₀Pd₇₀?at.%?alloy.An electrochemical sensor for the detection of ascorbic acid?AA?in neutral condition was constructed.The step time and step potential are optimized.The surface morphology,composition and structure of Net-AuPd were characterized by SEM,EDS,XPS and XRD.The electrocatalytic activity of Net-Au Pd electrode for AA oxidation is much better than that of Au and Pd electrode treated under the same conditions.Net-AuPd electrode has wide linear detection range?4?M?18.104 mM?for AA detection,as well as high sensitivity(934?A cm^-2 mM^-1)and long-time stability?3 weeks?.?4?A micro-nanostructured dendrite electrode?D-Au Ag?was prepared by square wave pulse method in H₂SO₄ electrolyte on the surface of a smooth Au₈₀Ag₂₀?at.%?alloy,and was used for the electrochemical detection of H₂O₂ in alkaline condition.The pulse time of the square wave is optimized.The surface morphology,composition and structure of D-AuAg were characterized by SEM,EDS,XPS and XRD.In alkaline condition,the effect of D-AuAg on the electroreduction of H₂O₂ is much better than that of the dendrite gold electrode?D-Au?.D-AuAg electrode has a wide linear detection range for H₂O₂?0.04?M?23.104 mM?and good long-term stability?4 weeks?.