title: Eosin Y-sensitized graphitic carbon nitride fabricated by heating urea for visible light photocatalytic hydrogen evolution: the effect of the pyrolysis temperature of urea.
abstract: Graphitic carbon nitride (g-C3N4) was prepared by pyrolysis of urea at different temperatures (450-650 °C), and characterized by thermogravimetric and differential thermal analysis (TG-DTA), elemental analysis (C/H/N), X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), Brunauer-Emmett-Teller (BET) analysis, Fourier transform-infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The samples prepared at low temperatures (450 and 500 °C) are a mixture of g-C3N4 and impurities, whereas the samples prepared at high temperatures (550, 600 and 650 °C) should be g-C3N4 (polymeric carbon nitride). The polymerization degree of g-C3N4 for the prepared samples increases to a maximum at 600 °C with increasing pyrolysis temperature and then decreases, whereas the defect concentration changes conversely, that is, g-C3N4 prepared at 600 °C has the lowest defect concentration. Using Eosin Y (EY) and the prepared sample as the sensitizer and the matrix, respectively, the photocatalytic activity for hydrogen evolution from aqueous triethanolamine solution was investigated. The g-C3N4 prepared at 600 °C exhibits the highest sensitization activity. Under optimum conditions (1.25 × 10(-5) mol L(-1) EY and 7.0 wt% Pt), the maximal apparent quantum yield of EY-sensitized g-C3N4 prepared at 600 °C for hydrogen evolution is 18.8%. The highest activity can be attributed to the pure composition, the higher dye adsorption amount and the lowest defect concentration.
authors.affiliation: Department of Chemistry, Nanchang University, Nanchang 330031, China.
authors.forename: Junying
authors.initials: J
authors.lastname: Xu
authors.forename: Yuexiang
authors.initials: Y
authors.lastname: Li
authors.forename: Shaoqin
authors.initials: S
authors.lastname: Peng
authors.forename: Gongxuan
authors.initials: G
authors.lastname: Lu
authors.forename: Shuben
authors.initials: S
authors.lastname: Li
mesh_terms: D002384:Catalysis; D004801:Eosine Yellowish-(YS) / Q000737:chemistry*; D006361:Heating; D006859:Hydrogen / Q000737:chemistry*; D008027:Light; D009570:Nitriles / Q000737:chemistry*; D055668:Photochemical Processes; D013696:Temperature; D014508:Urea / Q000737:chemistry*
chemical_list: D009570:Nitriles; C011206:cyanogen; D006859:Hydrogen; D014508:Urea; D004801:Eosine Yellowish-(YS)