Carbon-Based Nanocomposites For Photo/Electrocatalytic Activity

With the increasingly serious problems of environmental pollution and resource shortage,carbon peak and carbon neutrality have become the strategic goals to solve the future energy problems.One of the effective means to achieve this ambitious goal is to develop carbon-based nano-photo/electrocatalytic materials.Compared with precious metal and transition metal materials,carbon materials have the characteristics of large specific surface area,small specific gravity,adjustable photo/electrocatalytic activity,etc.,showing unique advantages in sensitized solar cells,photocatalytic degradation of organic matter,electrocatalytic water splitting to produce hydrogen and other aspects.In this paper,carbon quantum dots(CQD),graphene oxide(GO),fullerene quantum dots and fullerene nanorods were prepared by wet chemical method,and their photocatalytic and electrocatalytic properties were investigated.Specific research contents are as follows:(1)The composite of CQD,GO and polyaniline(PAN)was prepared by liquid phase method.The results showed that PAN/GO/CQDs had higher specific surface area,enhanced light absorption and stronger charge transport performance.The performance test results show that the sample loaded with carbon quantum dots(TG-DSSC)exhibits higher electron and charge transfer efficiency than the sample loaded with non-carbon subdots.The abundant porous structure in the bulk phase of the composite material promotes the mass transfer process and enhances the carrier concentration,thus improving the efficiency of the solar cell.In addition,the tests on the flexibility and durability of the device show that the strong interaction between GO and CQD and PAN substrate not only enhances the mechanical properties of the device,but also improves the electrical conductivity of the device.The resulting device exhibits large open-circuit voltage and filling factor,and finally improves the photoelectric conversion efficiency of the device.(2)New photocatalytic nanofibers PAN/GO,PAN/CQDs and PAN/GO/CQDs were synthesized by electrospinning.The photodegradation of methylene blue(MB)in water was studied by ultraviolet visible spectrophotometry.The results showed that the photodegradation efficiency of PAN/GO/CQDs nanofibers was the highest,and the photocatalytic degradation rate of MB reached 100%under 25 min of light.This improvement may be due to the reduction of charge transfer at the CQDs and GO interface by the composite,which attenuates photocorrosion.The high specific surface area of nanocomposites exposes more catalytic active sites,and the quantum effect of CQD improves the photoelectron-hole separation efficiency,thus enhancing the photodegradation efficiency of MB.Further study showed that pH value and dye concentration had significant effects on the photocatalytic performance.In addition,the reusability of PAN/GO/CQDs nanofibers confirms their great potential for industrial wastewater treatment.(3)Pectinase and cellulose acetate composite nanofibers(P-CNFs)were prepared by electrospinning.The morphology of P-CNFs nanofibers showed that they were uniformly arranged and inlaid with activated carbon particles.The addition of pectinase significantly affected the micromorphology of activated carbon,and the nanoconfined effect of multistage micropore structure effectively improved the degradation efficiency of P-CNFs on MB.The photodegradation experiment showed that P-CNFs could effectively degrade MB in neutral environment within 1 minute.At the same time,the obtained P-CNFs showed high adsorption capacity of heavy metal ions.Due to the large specific surface area,porous structure and a large number of unoccated hydroxyl,amino and other active sites on the surface of nanofibers,the adsorption capacity of lead ions is effectively improved,and the removal efficiency of lead ions can reach 80%.In addition,the composite has good stability and repeatability.P-CNFs is a promising material for the safe,simple and rapid removal of lead ions and MB dyes.(4)N-doped fullerene quantum dots were prepared by chemical oxidation method,and Co/CN composite catalyst materials were successfully prepared by loading cobalt on the surface.The optimum process parameters were obtained by adjusting the calcination temperature and the ratio of raw materials.Electrochemical tests showed that the samples treated at 600℃ had better electrochemical properties of HER and OER,and the required overpotential was 289 mV and 630 mV,respectively,when the current density of 10 mA cm-2 was reached.It also has the largest double-layer capacitance(Cdl)and electrochemical active surface area(ECSA).The charge transfer between cobalt nanoparticles and CN substrate enhances the charge density of Co site and effectively promotes the adsorption and dissociation process of water molecules,thus showing good electrocatalytic activity.(5)Fullerene nanorods were prepared by liquid-liquid interface method and coated with bimetallic layer hydroxides CoNi-LDH.After vulcanization,SF-NFrpvp/CoNi2S4 composite electrocatalyst was obtained.The effects of solvent effect,temperature and raw material ratio on the properties of catalyst were investigated.The results of electrochemical tests show that SF-NFR-PVP/CoNi2S4 has a large electrochemical surface area,good electrolytic performance of aquatic hydrogen,and the Tafel slope is only 82 mV dec-1,which is comparable to the noble metal IrO2.The PVP coating improved the hydrophilicity of the composite,promoted the adsorption process of water molecules,and the electron collector fluid effect of fullerene nanorods accelerated the interface charge transfer rate of CoNi2S4,which effectively improved the electrolytic performance of the electrocatalyst.