The Fabrication Of Butterfly-wing Architectured Electrode Materials And Their Electrochemical Properties

Micro/nano-architectured electrodes are frequently investigated and studied in electrochemical arena,due to their high specific surface area and energy density.Designing and fabricating electrode materials with micro/nano-architectures are of great importance to enhancing electrochemical reaction efficiency and electrode performances.However,the diversity of composition and architectures in various systems of current research impeded the comparison and investigation of architecture effect.What’s more,most as synthesized architectures are complex and disordered with poor controllability,which makes it impossible to describe the inner mass transfer behavior accurately and systematically.Hence,fabricating electrode materials with ordered micro/nano-architectures and investigating their electrochemical performance and mass transfer property,are of great theoretical and practical value for revealing the mechanism of architecture effect and further designing efficient electrode architectures.Butterfly is a creature with the most subspecies in nature.Butterfly-scales exhibit various complex architectures,most of which are in micro/nano-scale and highly ordered with good connectivity.This forms a giant architecture gallery,and provides great structural references and a natural template warehouse for the design and fabrication of electrode materials.This dissertation transferred butterfly wings with different elaborate micro/nano-architectures into electrode materials,investigated the influence on electrochemical behavior,selected the most effective architecture,constructed diffusion domain models,simulated the diffusion property of electrolyte in micro/nano-architectures,and directly described the mechanism of architecture effect on electrochemistry.The main contents are as follows:1.The mechanism of different butterfly-wing architecture affected electrode behavior was investigated through one-electron transfer process.The flat wing membrane and butterfly-wings with ridge array architecture and ridge/nano-hole array architecture were transferred into carbon electrodes using carbonizing-graphite coating method.Cyclic voltammograms of[Fe（CN）₆]^3-/4-were achieved on electrodes with different architectures.Compared to flat-electrode,the peak potential separation of ridge-and ridge/hole-electrode was decreased by 100 mV and 117 mV,respectively;the oxidative peak current density was increased by 6.0μA/cm² and 9.9μA/cm²,respectively.This indicates that butterfly-wing architectures,especially ridge/nano-hole array architecture,have obvious promotion for the efficiency of electrochemical reaction.Compared to one dimensional semi-finite diffusion to the flat electrode,the ridge-electrode exhibits additional lateral diffusion to the ridge wall;while the ridge/hole-electrode exhibits a more efficient“thin layer diffusion”behavior within the nano-hole area.This work reveals the mechanism of architecture affected electrochemistry,and provides theoretical basis and reliability demonstration for introducing butterfly-wing architectures into electrochemical systems.2.The influence of three different butterfly-wing architectures on the electrocatalytic behavior of methanol oxidation was investigated and compared,to achieve the most efficient architecture for electrodes.Morph butterfly-wings with lamellar-ridge architecture and Troides aeacus butterfly-wings with ridge array architecture and ridge/hole array architecture were transferred into platinum by electroless deposition method.The electrochemically active surface area（EASA）of lamellar ridge-Pt was 5.0 times of its flat counterpart;while the EASA of ridge-Pt and ridge/nano-hole-Pt was 2.4 and 4.3 times of their flat counterpart,respectively.As for the peak current density of methanol oxidation,the lamellar ridge-Pt,ridge-Pt and ridge/nano-hole-Pt was 5.2,2.7 and 3.9 times of their flat counterpart,respectively.This indicates that butterfly-wing architectures,especially lamellar ridge architecture,greatly enhanced the methanol electro-oxidation efficiency.According to further simulation,an efficient zigzag diffusion in the lamellar-ridge architecture and more efficient“thin layer diffusion”in the space of adjacent lamellae occurred for rapid methanol depletion.This work demonstrates how architectures influence the electrocatalytic behavior of electrodes through mass transfer,and confirms the lamellar ridge architecture as one of the most effective electrode architectures by comparing to other different butterfly-wing structures,which shows great application potential in the electrochemical arena.3.The influence of the above mentioned lamellar-ridge architecture on electrochemical detection performance was explored.Using Morph butterfly-wings as template,lamellar ridge-Au was fabricated by electroless deposition method,and modified on glassy carbon electrode（GCE）by Nafion for amperometric detection of glucose.The EASA and glucose oxidation current for lamellar ridge-Au electrode was4.8 and 5.4 times of its flat counterpart,respectively.The sensitivity for glucose detection under 0.21 V was increased by 5.8 times and the detection limit was lowered by 3.7 times compared to the flat electrode,showing prominent performance compared to previous reports.Simulation results demonstrate that the zigzag and“thin layer diffusion”behavior greatly promoted the transport and depletion of glucose,leading to wider linear range,higher sensitivity,and lower detection limit.This work introduced the butterfly-wing architecture into electrochemical detection arena,and provided a prototype and structural reference for the development of efficient sensor electrode.4.Sensor electrode with high interference tolerance was achieved by further treating the as synthesized lamellar ridge-Au via surface molecular imprinting.Thio-molecules and p-nitrophenol（p-NP）template molecules were modified on lamellar ridge-Au surface synchronously followed by removing p-NP template to achieve sensor electrode with specific p-NP recognition ability.Differential pulse voltammetry（DPV）was used to investigate the p-NP detection performance.Compared to the bare lamellar ridge-Au with poor selectivity,the surface imprinted lamellar ridge-Au sensor exhibit good selectivity for p-NP,the concentration linear range for detection was increase by two orders of magnitude,and the detection limit was decreased by 240 times,showing better performance than other works.This work coupled the surface molecular imprinting technology with butterfly-wing architecture to achieve electrochemical detection of specific molecules with high selectivity and high sensitivity.This method can be extended to other molecules,and is a successful example of applying butterfly-wing architectures into electrochemical detection system.5.Micro-array electrode was fabricated by electrodeposition on ordered butterfly-wing architectures,and its electrochemical detection performance was also explored.Carbonized butterfly-wings with inverse-V ridge architecture were used as substrate,and tip effect for electric field occurred when exerting a cathode potential.This provides a favorable condition for silver nucleation and grain growth along the ridge tips,and hence caused formation of regularly arranged microband arrays.The optimum condition was electrodepositing under the potential of-0.9 V for 90 s.The linear range for amperometric detection of hydrogen peroxide was 20μM²3 mM with a sensitivity of 27.1μA/（mM cm²）and a detection limit of 14μM.This electrochemical performance is prominent compared to previously reported Ag based sensors.Further simulation for the electric field distribution and Ag deposition process demonstrated that the mechanism of Ag microband array fabrication was the densely distributed electric field around ridge tips.The result also shows possibility for using other butterfly-wing architectures as electrodeposition substrate to obtain more elaborately arranged micro/nano-array electrodes.In summary,based on the structural pool of butterfly-wings and by combining experimental and theoretical simulation method,this paper provides a simple yet efficient and reliable way to choose effective micro/nano-architectures for electrode and reveal the mechanism for promoting electrochemical performance.These efforts may provide reference and prototype for future structural design of electrode materials with enhanced electrochemical performance.