Synthesis And Electrochemistry Of Heteroatom-doped Carbon Materials

Heteroatom doping has been an efficient method to enhanceelectrochemical performance of carbon material. Particularly, nitrogen (N) isreckoned as a peerless dopant, which could introduce more defects in the sp2hybridized C frameworks. Complementing N element, sulfur (S) is receivingincreasing attention in carbon materials research very recently, since S is easyto be polarized due to large lone pairs that could induce high chemicalreactivity of the carbon materials. Furthermore, recent density functional theory(DFT) calculation reveal the synergistic interaction of N-and S-co-dopingresulting from the redistribution of spin and charge densities in the HOMOstructure. However, the synthesis of heteroatom-doped carbons remainschallenging. In this work, we propose facile strategies for preparingheteroatom-doped carbons through one-step pyrolysis synthesis approach.The effect of heteroatom doping on the electrochemical activity weresystematically studied. The work was summarized as follows:(1) Synthesis of nitrogen-doped graphene (NG) and its lithium-storageperformance. A series of NGs were successfully achieved via facile thermalcondensation of glucose and dicyandiamide at different temperatures duringwhich dicyandiamide acts both as nitrogen source and sacrifice template.Devoid of surfactants or poisonous organic solvents, this small-moleculesynthetic approach is a simple and cost-effective way to obtain NG with highand tunable nitrogen doping level. Ascribing to their unique crumpled structure,large surface area and high pore volume, NGs were shown to be promisinganode material, manifesting high reversible capacity, excellent rate capability,and superior cycle performance. The effect of N content incorporated and nitrogen-doped type on the battery performance were systematicallyinvestigated.(2) Synthesis of N, S dual-doped porous carbon (N-S-PC) and itselectrocatalytic property. Herein, a one-step approach was proposed for thefirst time to synthesize N, S dual-doped porous carbon (N-S-PC) viaco-pyrolysis of sodium citrate and cysteine. Possessing unique porousstructure and large pore volume as well as good accessibility, N-S-PCdemonstrates significantly improved electrocatalytic activity toward oxidation ofascorbic acid (AA), dopamine (DA), and uric acid (UA). In the coexistingsystem, the peak potential separation between AA and DA is up to251mV,which is much larger than for most of the other carbo ns. On the basis of largepotential separation and high current response, selective and sensitivesimultaneous determination of AA, DA, and UA was successfullyaccomplished by differential pulse voltammetry, displaying a linear responsefrom50to2000μM, from0.1to50μM, and from0.1to50μM with a detectionlimit (S/N=3) of0.78,0.02, and0.06μM. This work highlights the importanceof N, S dual doping and hierarchical porous carbons for efficient catalysis.