Synthesis Of Double Non-metal Doped Carbon Dots And The Study Of Their Photo-/electro Properties

With the rapid development of the economy,the demand of energy is increasing.In view of increasingly energy demand,researchers have paid more attention to develop a green and highly efficient energy.Hydrogen is considered as one of the promising energy source because of its high conversion efficiency,recyclability and nonpolluting nature.Electrochemical or photoelectrochemical hydrogen evolution is one of the feasible methods to produce molecular hydrogen,but it requires benign and efficient electrocatalysts to lower the overpotential and minimize energy consumption.Therefore,it is urgent to search the efficient and low-cost catalyst for electrochemical hydrogen production in large quantity with low loss.Carbon nano material with unique physicochemical property has a great potential in catalysis,biology and sensor.In addition,doping nonmetal atoms into the carbon nano material can effectively improve the photoelectric property of original carbon nano materials.In this paper,we prepared nitrogen,phosphorus(NPCDs)and nitrogen,sulfur double non-metal co-doped carbon dots(NS-CDs)via the improved synthetic method,and we studied the fluorescence property of NSCDs.In addition,we prepared compound catalyst based on the double non-metal co-doped carbon dots and studied their photo/electro properties.The main works include the following parts:1:By a simple hydrothermal method,we synthesized nitrogen,phosphorus co-doped carbon dots and cobalt disulfide(CoS2)compounds(NPCDS/CoS2).We applied it to be the electrocatalyst for hydrogen evolution reaction(HER).Integrating the results of X-ray photoelectron spectroscopy(XPS)and infrared spectrum,we found a new characteristic peak which was assigned to Co-O-C bonding.Electrochemical test results showed that NPCDS/CoS2 compounds was the best catalytic activity compared with the single doped carbon dots and CoS2 compounds.In acidic medium(0.5 M H2SO4),NPCDS/CoS2 catalyst exhibited a small potential?82 mV,a small Tafel slope-76 mV/decade and a long term stability.Further research proved:the excellent HER performance might be attributed to the existence of Co?O-C bonding,which improving the efficiency of electronic transmission and N,P co-doping can effectively improve the electronic structure of carbon.2:We synthesized N,S co-doped CDs by hydrothermal treatment of L-cys,citric acid in high pressure reactor.The obtained NSCDs were used as lable free fluorescent probes to detect the concentration of hydrogen peroxide(H2O2)and reduced glutathione(GSH).The detection limit of H2O2 was as low as 0.10 ?M and the detection limit of GSH was as low as 1.00 × 10-6 M.Experimental results indicated that the fluorescent property was correlative with surface functional group on CDs.3:We synthesized the nitrogen,sulfur co-doped carbon dots and CoS compounds(NSCDs/CoS)as the electrocatalyst for HER.We optimized the catalytic activities by adjusting the concentration of NSCDs and the pyrolysis temperature.Among them,the catalyst with the NSCDs amount of 20 mg/L and the pyrolysis temperature at 450?exhibited the best electrocatalytic activity towards HER,featured by a small onset potential of?0.095 V,a small Tafel slope of 56 mV/decade and a good stability in 0.5 M H2SO4.We suggested the excellent electrocatalytic activity of NSCDs/CoS for HER may be attributed to the high charge transfer efficiency between NSCDs and CoS via Co-S-C bonding,and the enhanced surface area could accelerate the catalytic activities.