Applied Catalysis B: Environmental 115–116 (2012) 81–89 Contents lists available at SciVerse ScienceDirect Applied Catalysis B: Environmental jo ur n al homepage: www.elsevier.com/locate/apcatb One-step, hydrothermal synthesis of nitrogen, carbon co-doped titanium dioxide (N,C TiO 2 ) photocatalysts. Effect of alcohol degree and chain length as carbon dopant precursors on photocatalytic activity and catalyst deactivation D. Dolat a , N. Quici b , E. Kusiak-Nejman a , A.W. Morawski a , G. Li Puma b,∗ a West Pomeranian University of Technology, Szczecin, Institute of Chemical and Environmental Engineering, Pulaskiego 10, 70-322 Szczecin, Poland b Photocatalysis and Photoreaction Engineering, Department of Chemical Engineering, Loughborough University, Loughborough, LE11 3TU, United Kingdom a r t i c l e i n f o Article history: Received 30 October 2011 Received in revised form 30 November 2011 Accepted 3 December 2011 Available online 9 December 2011 Keywords: Photocatalysis TiO2 Degradation Nitrogen/carbon co-modification Catalyst lifetime Intrinsic photocatalytic activity Volumetric rate of photon absorption a b s t r a c t A one-step, hydrothermal method for the synthesis of nitrogen, carbon co-doped titanium dioxide (N,C TiO 2 ) photocatalysts is demonstrated. The incorporation of nitrogen from ammonia and car- bon from alcohols with different chain length (methanol, ethanol, isopropanol, 1-butanol, 2-butanol, tert-butanol) used as carbon precursors was confirmed by FTIR/DRS and XPS analyses. The UV–vis/DR absorption spectra of the modified photocatalysts extended into the visible. XRD, BET and Zeta Sizer- Nano techniques were used for the characterization of the modified photocatalysts. The crystallite size of N,C TiO 2 was not affected by the nature of the alcohol or the pressure acquired during the modification process but surface area, particle size (crystal agglomerate) and anatase content increased with synthesis pressure. In contrast with other studies in literature, the photoactivity of the different synthesized mate- rials was evaluated at a constant volumetric rate of photon absorption (VRPA) in an annular photoreactor. This innovative method allows the evaluation of the intrinsic photoactivity of each material. As a result, the effect of N,C-co-modification on the TiO 2 photoactivity was evaluated without interference from the amount of radiation absorbed by each suspended powder since the total radiant energy absorbed by each slurry suspension was kept constant. Phenol decomposition confirmed that activity increased with the chain length of the alcohol precursor. The highest intrinsic photoactivity was for N,C TiO 2 pre- pared from 2-butanol, and 1-butanol as carbon precursor which also exhibited much stronger resistance to deactivation during multiple catalyst reuse compared to pristine TiO 2 and commercial Degussa P25 photocatalysts. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Titanium dioxide (TiO 2 ) is a widely used photocatalyst for water treatment, air purification, antibacterial, deodorization, self- cleaning coating or anti-stain applications [1–5]. The irradiation of TiO 2 with band gap photons produce electron–hole couples which after migration to the surface of the solid may be trapped by surface reducible species (e.g., molecular oxygen) and adsorbed water to produce superoxide anion radicals and hydroxyl radi- cals. Subsequent reactions of these radicals between themselves and with adsorbed molecules lead to oxidation/reduction reactions which in turn may degrade aqueous/air pollutants. The band-gap of TiO 2 (anatase) is 3.2 eV, in consequence photons of wavelength of 384 nm or less (UV-A) can promote the generation of electron–hole couples. However, the redox process is limited by electron–hole recombination which in practice reduces the effectiveness of TiO 2 ∗ Corresponding author. Tel.: +44 0 1509222510; fax: +44 0 1509223923. E-mail address: g.lipuma@lboro.ac.uk (G. Li Puma). as a photocatalyst. The narrowing of the band gap in TiO 2 and its modification allows the utilization of a wider fraction of visible light for the production of charge carriers. Metal ions (Pt, Au, Ag, Cu, Fe), metal oxides (SnO 2 , WO 3 , MnO 2 , V 2 O 5 ) and nonmetals (C, N, F, S, P) have been proposed as modifiers that improve the photoactiv- ity of TiO 2 [5–14]. Nitrogen and carbon doped into substitutional sites of TiO 2 [15] results in narrow band gaps (red-shift) which may lead to higher photo-response and higher photocatalytic activity. In other studies it is revealed that doped TiO 2 undergoes elec- tronic transitions from localized states near the valence band to their corresponding excited states for Ti 3+ centers after visible light irradiation [[16] and reference therein]. Co-doping of titania with carbon and nitrogen simultaneously [17–28] may also show syner- gistic effect. In the study by Yin et al. [17] N and C co-doped titania prepared by a mechano-chemical method revealed very high photocatalytic activity for nitrogen monoxide degradation under visible light irradiation, possessing two absorption edges around 400 nm and 540 nm. Chen et al. [18] synthesized TiO 2 photocatalysts with dif- ferent amounts of carbon and nitrogen by the sol–gel method. The 0926-3373/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2011.12.007