Glucose Oxidase Membraneless Biofuel Cells And Their Performance Optimization

Enzymatic biofuel cells(EBFCs),as a kind of emerging green energy,are able to convert chemical energy into electrical energy by using enzyme as catalysts for the oxidation-reduction reactions of biofuels.Since biofuels(such as glucose or lactate)are common in nature and biological fluids of human beings,EBFCs can not only release the increasing energy crisis,but also hold wide application prospects in the area of wearable and implantable electronic devices.With the development of nanomaterials,the performance of EBFCs has been obviously improved.However,it is still difficult to meet the requirements of practical application.Aiming at the problem of low energy output of EBFCs,effective solutions of improving the performance of EBFCs had been explored in this paper.On the one hand,a new nanomaterial and a porous structure with good breathability were developed for improving the oxygen(O2)diffusion and electron transfer in EBFCs devices.On the other hand,the optimization of electrode arrays and structures of membraneless EBFCs devices were studied.The main research contents are as follows:(1)Based on the reaction principle of EBFCs,a EBFCs device was developed by the screen-printing technology.The fabrication of electrode substrates was achieved by screen printing carbon paste.And electrodes and EBFCs devices were designed in the standardized way for good consistency.In this experiment,the structure of membraneless EBFCs devices was designed and the influences of O2 concentration on the performance of EBFCs were studied.Furthermore,the impacts of connection type on overall output of EBFCs packs under air state were explored.As a result,the light emitting diodo(LED)could be lighted by connecting external power management system with EBFC s packs.The designed EBFCs device based on the screen-printing technology was easy prepared and could be connected by series and parallel to meet the requirement of different loads.Consequently,it was able to promote the development of stack structure and miniaturization of EBFCs devices.(2)Slow electron transfer and low reaction efficiency caused by insufficient O2 supply are the two main obstacles limiting the development of EBFCs.In order to enhance the performance of EBFCs,improve the O2 distribution in EBFCs devices and facilitate the electron transfer between the activity center of enzyme and the electrode surface,the membraneless EBFCs based on the carbon nanotubes(CNTs)/gold nanoparticles(AuNPs)hybrid with breathable electrodes were developed.Thereinto,carbon papers were selected as breathable substrates for the membraneless EBFCs owing to their good air permeability and electronic conductivity.In the bioanode,the CNTs/AuNPs hybrid was fabricated by reduction of AuNPs from chloroauric acid(HAuCl4)on CNTs,which exhibiting the uniform distribution of AuNPs as well as a three-dimension(3D)porous structure.Therefore,the hybrid could facilitate the electron transfer and improve the distribution and storage of O2.Additionally,the hybrid could provide appropriate microenvironment and strong adsorption for enzymes.In the cathode,platinum was applied as the catalyst not only for the reduction of O2,but also for the decomposition of hydrogen peroxide(H2O2).In this way,the H2O2 produced in the bioanode would be decomposed to generate O2 and thus be reutilized in both anode and cathode.For the assembled EBFCs device,because of the improved O2 distribution and fast electron transfer,it could show an open circuit potential(OCP)of 0.49 V and a maximum power density(MPD)of 244.66 cm-2 under natural air state.Moreover,the EBFCs device exhibited good stability.(3)In order to further improve the output performance of EBFCs devices and develope their practical applications,the influences of electrode shape and electrode array on the outputs of EBFCs were investigated by finite element analysis.Firstly,electrode models based on three electrode shapes(circle,hexagon and square)were constructed to explore the relationship between electrode shapes and the distribution of field strength and potential.As a result,circular electrodes would be the best choice for EBFCs because there were few influences of edge effects.Secondly,according to the characteristics of EBFCs devices,two structures of bipolar plate and monopolar plate were designed.According to the comparision of simulation results,the current densities and MPD of circular electrodes were maximum,and the hexagonal close-packed arrays were able to obtain maximum electrode areas and thus maximum total power output.For the monopolar plate EBFCs,anodes and cathodes were interlaced on the same plate in order to avoid the negative effects of bipolar plates on wearable and implantable devices.The interdigital distribution of anodes and cathodes could enhance the current output,while the series-parallel connection was able to increase the current and potential output at the same time.At last,topology theories applied in networks were extended to the design of electrode array in EBFCs.Three types of electrode array corresponding to radial,star and ring topologies were designed and analyzed.The electrode shape and electrode array studied in this paper would be of great significance to the structural design of EBFCs devices.