The Biological Fuel Cell Research, Direct Electrochemistry Of Enzymes And Proteins

As the fast growth of economy in the 21st century,environment pollution and energy crisis have been the two problems all the world must face.The exhausting conventional energy could not meet the need of continuous country economy growth. So,exploring new energy has been a particularly urgent task.Biofuel cell is a really new green environmental-protecting power source developed in the recent years.As a small power source,the application of biofue cell in some fields has been particularly attractive.However,the low output power density is the main problem which confines the further development of biofuel cell.One of the effective method to solve this problem is to explore appropriate carrier materials and immobilization methods of biocatalyst and realize the direct fast electron -transfer between the biocatalyst and the electrodes.In this thesis,the anodic catalyst and the cathodic catalyst in the biofuel cells have been fabricated on the basis of exploring the new carrier materials and enzyme immobilization methods.The main results and conclusions obtained are summarized as follows:1.Carbon black(CB) was widely used in many fields due to its good conductivity, large surface area and low cost etc.Spectrometric technique indicated that the oxygen-contained groups for example C=O and C-OH were present on the surface of CB powders.These groups can supply the favorable microenvironment for the immobilization and favor the electron-transfer of enzyme.In this work,CB was used as the carrier of glucose oxidase(GOx),hemoglobin(Hb).The adsorption method was used to immobilize GOx,Hb on the surface of carbon black powders and the Nafion was used to fix the catalyst.The direct electrochemistry and the electrocatalytic activity towards theβ-D(+)-glucose and H₂O₂ was also investigated.The stability of the electrode was studied.The FTIR spectroscopic and electrochemical measurements demonstrated that GOx could be immobilized on the surface of CB using a simple adsorptionmethod.The electrochemical measurements indicated that GOx immobilized on CB could undergo the quasi-reversible and direct electrochemical reaction and keep the bioelectrocatalytic activity for the glucose oxidation.Its formal potential,E^0',is -0.436 V and the electron transfer rate constant k_s value was estimated to be 0.800 s^-1,which is thirty times larger than those obtained for GOx repoted previously.This maybe be attributed to the oxygen-contained groups on the CB,such as -COOH and-OH groups.These groups can supply the favorable microenvironment for the immobilization of enzyme.Even after conservation for two weeks,its electrocatalytic activity decreased only 5%,illustrating the good stability of GOx immobilized on CB.The FTIR spectrum,UV-Vis spectroscopy and XPS spectra showed that secondary structure of Hb immobilized on the surface of CB was not destroyed and Hb retained its biological activity.The CV experiment results demonstrated that immobilized Hb could undergo a direct quasi-reversible electrochemical reaction.Its formal potential,E^0',is -0.330 V in phosphate buffer solution(pH 6.9) at a scan rate of 100 mV/s and is almost independent of the scan rate in the range of 40-200 mV/s.The electron transfer rate constant k_s value was estimated to be 1.02 s^-1,which is larger than those obtained for Hb immobilized on Au-colloid-cysteamine-modified gold electrode(0.49 s^-1),Hb modified CNT powder microelectrodes electrodes(0.062 s^-1),indicating a reasonably fast electron transfer between the immobilized Hb and the underlying electrode.The surface concentration (F) of Hb was 3.55×10^-9 mol/cm².The above results showed that as the carrier of enzyme,CB is promised to have wide application in the future.The method presented here is simple and effective and can be easily extended to immobilize and obtain the direct electrochemistry of other enzymes or proteins.2.In order to realize the effective realize the direct electron -transfer of biocatalyst (enzyme and proteins) and electrode,a whisker-like carbon composite(MCWC) was fabricated.The adsorption method was used to immobilize Hb on the surface of MCWC.Spectrometric technique indicated that immobilized Hb retained its native structure.The cyclic voltammetric results showed that immobilized Hb could undergo a direct quasi-reversible electrochemical reaction and has good bioelectrocatalytic activity and good stability for the reduction of H₂O₂.The electron transfer rate constant,ks,is 2.07 s^-1,which is larger than that on some other carriers reported previously.The surface concentration of Hb is 4.56×10^-13 mol/cm²,which is lager than 1.32×10^-13 mol/cm² on carbon black.This maybe because that the special carbon thorns structure can increase the specific area of adsorption,moreover,the numerous "V-type" channels formed among the thorns facilitates the fast diffusion of products. In addition,the oxygen-contained groups,such as -COOH groups and-OH groups can supply the favorable microenvironment for the immobilization of enzyme.Using the same method,the direct electrochemistry of Laccase on the MCWC was also studied.The electron transfer rate constant k_s value was estimated to be 0.77 s^-1 and the surface concentration(Γ) of Lac was 2.73×10^-12 mol/cm².The above results showed that as the new carrier of enzyme,MCWC is promised to be used widely in the fabrication of the biocatalyst of biofuel cell.3.Besides the carbon material,silica mesoporous sieves also could be used as carriers of biocatalyst in biofuel cell.3D large cage-like mesoporous silica sieves FDU-12 can be used as the carrier of horseradish peroxidase(HRP) due to its large cage size, appropriate entrance size and good biocompatibility.Spectrometric technique indicated that immobilized HRP retained its native structure.The cyclic voltammetric results showed that immobilized HRP could undergo a direct quasi-reversible electrochemical reaction and has good bioelectrocatalytic activity and good stability for the reduction of H₂O₂.The electron transfer rate constant k_s value was estimated to be 1.20 s^-1,indicating fast electron transfer between the immobilized HRP and the electrode.The surface concentration(Γ) of immobilized HRP was 5.44×10^-11 mol/cm², which was twice larger than the single layer adsorption concentration of HRP(2×10^-11 mol/cm²).This maybe be attributed to the 3D uniform pore structure of FDU-12 which facilitated the fast diffusion of products and provided favorable microenvironment for HRP.Large cage-like mesoporous silica sieves FDU-12 was promised to provide new idea for the direct electrochemistry of enzyme and development of new biofuel cell and biosensors...