Enhanced visible-light-driven photocatalytic activity of mesoporous TiO2−xNx derived from the ethylenediamine-based complex

Abstract

A facile solvent evaporation induced self-assembly (SEISA) strategy was developed to synthesize mesoporous N-doped anatase TiO 2 (SE-meso-TON) using a single organic complex precursor derived in situ from titanium butoxide and ethylenediamine in ethanol solution. After the evaporation of ethanol in a fume hood and subsequent calcinations at 450 C, the obtained N-doped TiO 2 (meso-TON)anatase was of finite crystallite size, developed porosity, large surface area (101 m 2 g À1) and extended light absorption in the visible region. This SE-meso-TON also showed superior photocatalytic activity to the SG-meso-TON anatase prepared via sol-gel synthesis. On the basis of characterization results from XRD, XPS, N 2 adsorption-desorption and ESR, the enhanced visible-light-responsive photocatalytic activity of SE-meso-TON was assigned to its developed mesoporosity and reduced oxygen vacancies. IntroductionMotivated by the discovery of the excellent visible-lightresponse of nitrogen-doped TiO 2 (TiO 2Àx N x , hereaer, TON),various nonmetal dopants (e.g. N, C, S, P, and halogen elements) have been extensively attempted to be doped or codoped into the TiO 2 matrix for narrowing its wide bandgap ($3.2 eV) and thus harvesting visible light. 3 Among those doped TiO 2 materials, TON is more desirable due to its low energy requirement for doping and superb performance in photovoltaic and photocatalytic applications.2,4-7 In practice, the mesoporous TON (meso-TON) is plausible because its large specic surface area (SSA) and developed porosity favour solar energy conversion. 4,8 Despite the fact that enormous advances have been achieved in the control of N-doping level, morphology, crystallite size and crystallinity of TiO 2Àx N x , 9-11 synthesis of mesoporous TiO 2Àx N x (meso-TON) remains a great challenge because the mesoporous structure is prone to collapse during nitriding and crystallization at elevated temperature. 8,12-14Ammonolysis is the most used nitriding technique for preparation of TON, though it occurs above 500 C. 2,10,13 Such a high ammonolysis temperature inevitably destructs the porosity of the primitive meso-TiO 2 , induces phase transition and hampers its applications in thin lm devices.2,10 In order to retain its developed porosity, a few low-temperature methodologies, such as sol-gel, 9 hydrothermal or solvothermal combined with post-nitriding, 10,11 have been developed for preparing meso-TON. In those methodologies, the involved solvent, surfactant template and chemical sources of Ti and N controlled the hydrolysis, nitriding and crystallization processes and thus determined the mesoporosity of the resultant TON. 15,16 In particular, the alternative nitrogen sources to NH 3 , such as NH 4 Cl, 13 urea, 15,17,18 HMT, 19 glycine 16 and thiourea, 20 are plausible for realizing low-temperature nitriding. Solvent evaporation induced assembly (SEISA) has been demonstrated to be an excellent route to prepare meso-TiO 2 thin lms, 12 in terms of its great exibility in handling the synthesis system (solvents, su...

Hybridising nitrogen doped titania with kaolinite: A feasible catalyst for a semi-continuous photo-degradation reactor system

“…Our BET results show that the specific surface area increased from (101), (004) and (200) [10]. Other studies also reported the absence of Ti-N crystal peak in the XRD patterns for their N-doped TiO 2 particles [7,8,18,19].…”

Visible-light photocatalysis on C-doped ZnO derived from polymer-assisted pyrolysis

“…Despite the fact that suitable amount of O vac can extend light absorption into visible light region and improve photocatalytic activity, the photoreactivity will drop dramatically if O vac concentration is greater than certain amount. 15,23 In this research, the C-doping level is quite high with almost 4.3 at.% carbide-based C 4À coexisting with comparable amount of O vac in the C-doped ZnO. Hence, the low visible-light-driven photocatalytic activity on the C-doped ZnO was tentatively assigned to the synergistic consequences of the overloaded C-dopants and O vac that favour the recombination of photogenerated charge carriers under irradiation.…”

“…Besides bandgap light absorption, visible-light absorption on the C-doped ZnO is also tailed beyond 800 nm which is a typical red shi induced by impurity adsorption or oxygen-vacancies (O vac ). 15,23 Advanced characterisations are necessary to determine C-species and O vac for understanding the nature of visible-light response on the C-doped ZnO.…”

“…1,5,11,12 Motivated by the success in the enhanced visible-light response of non-metal-doped TiO 2 , non-metal-doped ZnO photocatalysts have been extensively attempted because the non-metal (S, N or C) dopants can extend visible light absorption signicantly and well suppress photogenerated charge recombination at suitable doping level. 7,9,[13][14][15][16][17][18][19] C-doped ZnO is an emerging visible-light-responsive photocatalyst with desirable performance in cleaning up waste water, water splitting and photoelectrochemical cells. [7][8][9]11,20 Although synthesis of C-doped ZnO represents a considerable challenge, a few methodologies have been successfully established, including self-doping via thermal decomposition of Zn 5 (CO 3 ) 2 (OH) 6 precursor, 7 pyrolysis of Zncontaining inorganic-organic presursors, 8,14 polymer or carbon templated syntheses, 9 metal organic chemical vapour deposition (MOCVD) 21 and thermal plasma in-ight carbonisation techniques.…”

“…It is well known that photocatalysis follows the rst order kinetics law, so that the apparent reaction kinetics constant, k, can be extracted from the slope of plot of Àln (c/c 0 ) vs. reaction time. 7,14,15 The calculated k values for ZnO and C-doped ZnO are 0.009 and 0.006 min À1 , respectively. ZnO possesses better activity and larger k ZnO than C-doped ZnO, suggesting the visible-light-driven MB photodecomposition should not be dominated by bandgap excitation.…”