| Enzymatic biofuel cell is a new type battery using enzymes as catalysts.Biofuel cells have broad prospects due to their good biocompatibility,ability to operate at room temperature and pressure,environmentally friendly feature and available for implantable or wearable devices etc..Enzymatic electrode is the core component of enzymatic biofuel cell.It is a device that generates current by catalyzing oxidation or reduction substrates utilizing enzymatic catalysis.Enzymatic electrodes and their construction methods directly determine the performance of enzymatic biofuel cells.However,the output performance and stability of enzymatic electrodes do not meet the requirements of practical use.This is because the non-conductivity of the enzymatic protein shell loaded on the enzymatic electrode prevents the transmission of electrons,and the enzyme is easy to fall off or inactivate in the preparation and use process,thus affecting the output performance and stability of the enzymatic electrode,leading to the failure of large-scale production and application of the enzymatic biofuel cell.For soloving the problems,the three-dimensional enzymatic electrodes based on nickel foam,gold deposition layer and embedded immobilization method are designed and fabricated,and three enzymatic biofuel cells based on these enzymatic electrodes were assembled.This investigation can provide a reference for the design of high-efficiency enzymatic electrode and the assembly of enzymatic biofuel cell,and lay a foundation for the application of enzymatic biofuel cell in implantable and wearable equipments.The paper has three main aspects:1.The three-dimensional nickel foam is employed as substrate.The graphene and gold nanoparticles with excellent conductivity are modified on the substrate,then immobilized glucose oxidase,electron mediator and laccase by covalent bond on the electrode surface,constructed an enzymatic anode with three-dimensional double electron transfer channels,fabricated an enzymatic cathode with three-dimensional direct electron transfer,and successfully applied to a new glucose/oxygen enzymatic biofuel cell.The results show that the loading capacity of glucose oxidase on the anode surface can be significantly increased by using a three-dimensional foam nickel substrate.The loading density can reach to 4.03×10-7mol cm-2,23 times than that of the planar electrode,and the electron transfer rate constant of the GOx/Fc CA/Au-r GO/Ni enzymatic anode reaches 0.16 s-1,which is 7 times higher than that of the similar electrode.Under ideal operating conditions,the maximum output power density of the cell can reach to 2.84±0.09 mW cm-2.After 60 days of continuous operation,the output power can still reach 86.3%of the initial value.In human blood,the maximum output power of the biofuel cell is 0.39±0.04 mW cm-2.It can be seen that the electrodes have the advantages of high enzymatic loading,good stability,outstanding activity and remarkable electron transfer rate.The biofuel cell has the advantages of high output power and good stability,and is expected to be applied in implantable devices.2.For further improve the stability of the enzymatic electrode and the corresponding enzymatic biofuel cell,three-dimensional carbon felt with more stable chemical properties is employed as substrate.The three-dimensional conductive network of enzymatic anode and cathode is constructed by modifying gold nanoparticles on the surface of the electrodes,and then using the surface microporous structure of quaternary ammonium salt cationic modified perfluorosulfonic acid resin to embed glucose dehydrogenase and bilirubin oxidase.The enzymatic anode and cathode are assembled into a three-dimensional membrane-free glucose/oxygen biofuel cell.The results show that the enzymatic loading of the electrode is5.37×10-8 mol cm-2,at least three times larger than that of the planar electrode,and the stability of the enzymatic anode and cathode after 60 days storage could maintain 97.8%and97.6%of their initial values,respectively.Under ideal operating conditions,the open circuit voltage of the cell is 0.85 V,and its maximum output power can reach 0.0219±0.00013 mW cm-2.After 60 days of continuous operation,the performance of the enzymatic biofuel cell remains 90.3%of its initial value.Therefore,the electrodes have the advantages of excellent stability and high effective enzymatic loading;the cell has the advantages of great open circuit voltage and remarkable stability,and has potential application value in implantable devices.3.Using the ultra-thin flexible nickel foam with larger surface area as the substrate of the electrode,the gold deposition layer is modified on the surface,and the three-dimensional conductive network is fibricated.Then,the flexible enzymatic anodes and flexible enzymatic cathodes are prepared by covalent immobilization of glucose oxidase and laccase.The two flexible enzymatic electrodes are assembled with cellulose acetate membrane,agarose hydrogel electrolyte and silicone rubber.for developing a flexible glucose/oxygen biofuel cell.The research shows that the gold deposition layer makes the surface of the nickel foam skeleton coarser,improves the apparent surface area of the nickel foam,and reduces the electron transfer resistance of it,and its resistance decreases from 55.7Wto 30.6Wcompared with the bare nickel foam,which is reduced by 45%.The three-dimensional gold modified nickel foam structure increases the enzymatic loading of the electrode to 5.68×10-7 mol cm-2,leading to the short-circuit current density of the cell increases to 9.04 m A cm-2 under ideal operating conditions.The maximum output power density of the flexible enzymatic biofuel cell can reach to 2.32±0.07 mW cm-2,and its output performance can remain 84.6%after 60days.Its output performance remains very stable in bending condition or after 1000 bending.Thus the electrodes have the advantages of low electron transfer resistance and high enzymatic loading.The enzymatic biofuel cell has the advantages of good short circuit current density,outstanding maximum output power,remarkable stability and high bending performance,and has potential application value in wearable devices. |
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