Preparation And Application In Microbial Fuel Cells Of Xylose-Based Carbon Dots

Biomass resources with wide sources,low cost,natural non-toxic and other characteristics,very competitive economy.Xylose often exists in hemicellulose in a bound state and is the second largest carbohydrate component in plants.At present,the research based on cellulose components of forest trees is very extensive,and there are few studies on xylose of hemicellulose,so this paper focuses on the application value of xylose components.Microbial fuel cell is a device that converts chemical energy of organic substrates into electric energy using electroactive bacteria.It is a new technology in green energy production in recent years.However,the application of forest tree glycosyl components in this technology is mainly as organic substrates and carbon sources,and the work of promoting microbial fuel cell power generation is relatively little.Therefore,this paper proposes to construct xylosyl carbon dots to improve the electricity generation performance of microbial fuel cells and explains the relevant mechanism.Specific research contents are as follows:(1)Two xylose-based carbon dots(D-CDs and M-CDs)were prepared by a simple onestep hydrothermal method using xylo-oligosaccharide and xylose as raw materials and dopamine hydrochloride as nitrogen source,respectively.The morphology,structure and optical properties of glycosyl carbon dots were characterized by microscopy,energy spectrum and spectrometer.The two kinds of carbon dots show quasi-spherical morphology.They are mainly composed of three elements,C,O and N;The surface is rich in oxygen and nitrogen functional groups.The photoluminescence emission of the two carbon dots are located in the green light region,which have excitation dependent fluorescence behavior.The two kinds of CDs all have good biocompatibility.It is found that M-CD has more significant conjugated structure than D-CDs.(2)Application of D-CDs in microbial fuel cells(MFCs)of classical electric-producing bacteria S.oneidensis and non-classical common bacteria.The results showed that D-CDs effectively accelerated the extracellular electron transfer rate of S.oneidensis and E.coli,and accelerated the metabolism level of microorganisms,so as to effectively improve their electrical performance.Among them,the maximum current value and cumulative charge of MFCs of S.oneidensis incubated with D-CDs increased by about 6 times and 5 times respectively.This result lays a preliminary foundation for the synergistic effect of xylose-based carbon dots and microorganisms to promote electricity generation.(3)Furthermore,the synergistic interaction between M-CDs and microorganisms with more obvious conjugated structure was used to promote electricity generation efficiently.The results showed that M-CDs promoted microbial electricity generation more efficiently than DCDs.The maximum current value and cumulative charge of MFCs of S.oneidensis incubated with M-CDs increased by about 12 times and 8 times respectively.The maximum current value and power output of MFCs of M-CDs incubated Escherichia coli increased by 94 times and172 times compared with the blank control group.A detailed study of the related mechanisms showed that M-CDs could be taken up by microorganisms and construct electron transport channels inside microorganisms to accelerate electron transfer within bacteria,between bacteria and between electrode interfaces.The acceleration of electron transport rate increases the REDOX reaction rate of microbial protease,which in turn metabolizes more electrons.The results further provide scientific basis and research basis for promoting microbial electricity generation by xylose-based carbon dots.