Template-free synthesis of mesoporous N-doped SrTiO3 perovskite with high visible-light-driven photocatalytic activity

Abstract

An effective, template-free synthesis methodology has been developed for preparing mesoporous nitrogen-doped SrTiO 3 (meso-STON) using glycine as both a nitrogen source and a mesopore creator. The N-doping, large surface area and developed porosity endow meso-STON with excellent activity in visible-light-responsive photodegradation of organic dyes.The exceptional electro-optical properties and physicochemical stability of the perovskite SrTiO 3 (STO) give rise to its attractive performance in photocatalytic applications of solar power, including photocatalytic degradation of organic pollutants, water splitting and photoreduction of CO 2 .1-3 However, the intrinsic large bandgap energy (E g = 3.2 eV) of SrTiO 3 allows only the utilization of UV light, encompassing approximately 5.0% energy of the sunlight. 4 A variety of transition metals (TM) have been doped into a STO's crystal matrix in efforts to tune its electronic bandgap for harvesting visible light. 5,6Unfortunately, TM-doping can also bring about either phase impurity or fast recombination of photogenerated charge carriers. Nonmetal-doping represents another effective strategy to realize visible-light response.7-9 Indeed, it was found that N-doped SrTiO 3 (SrTiO 3Àx N x , STON) exhibited excellent photoreactivity and stability under visible-light irradiation. 10Mesoporous-structured photocatalysts are highly desirable in photocatalysis since their large specific surface area (SSA) and mesoporous channels greatly facilitate adsorption, diffusion and surface reaction of the reactants.11 STO perovskite belongs to the cubic crystal system, and typically has low SSA and poor porosity. Moreover, the porosity of STO could be further destroyed by the known processes of nitriding STO to STON. 5,12Although mesoporous STO has been prepared via templatedirected synthesis using various soft (e.g. surfactant or polymer 13 ) and hard (e.g. inorganic salts 14 ) templates, the synthesis of mesoporous STON has rarely been achieved.Here we report a novel, template-free synthesis methodology to prepare mesoporous STON using glycine as both a nitrogen source and a mesopore creator. Aqueous solution of glycine and Sr(NO 3 ) 2 was dropped into ethanol solution of titanium butoxide under stirring, followed by solvent evaporation and subsequent calcinations at 550 1C for 2 hours. The obtained STON was characterized by XRD, TEM, FTIR, UV-vis, and XPS techniques and used for the photodegradation of three refractory organic dyes under visible-light irradiation.Only a strong single peak appears in the small angle XRD pattern (Fig. 1) of the STON sample, suggesting that it possesses disordered wormlike mesopores. 15 The TEM image in Fig. 2A nicely confirms such mesoporosity. The HRTEM image inserted in Fig. 2A reveals that the walls of the mesopores are comprised of single crystal perovskite STON. The labelled lattice distances are consistent with those of (100) and (110) diffractions obtained from XRD tests (Fig. S1, ESIw). In contrast, the STO sample presents poor mesoporous featu...

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

“…However, broad N 1s peaks appear within 397-402.5 eV for the meso-TON materials, which can be attributed to different nitrogen species, such as substitutional NO x (Ti-(NO) x , 398.7-399.5 eV) and interstitial NO x (398.2-398.5 eV and 400-402 eV). 16,32 Such broad N 1s XPS spectra due to various NO x -dopants have ever been observed in the N-doped TiO 2 .…”

“…5B, while broadening of O 1s at 531 eV can be clearly observed which was previously attributed to the presence of the N-Ti-O and O-N-Ti-O bond. 13,16,33 The broadening of O 1s spectra in 531-532.5 eV may be assigned to the surface hydroxyl groups on titania. The three samples are of very similar C 1s XPS spectra centred at 285 eV (Fig.…”

“…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, surfactant templates and precursors).…”

“…16,39 The principal rhombic ESR signals (Fig. 6) of SE-meso-TON and SG-meso-TON are very similar, and their characteristic g tensors at approximately 2.0034 can be assigned to the single-electron-trapped oxygen vacancies ðV In comparison to the major ESR signals in Fig.…”

Effect of Cation/Anion Co‐doping on the Photocatalytic Performance of Na3SbO(PO4)2

“…Three new bands around 1630, 1490, and 1330 cm -1 were observed for nitrogen doped compounds which are characteristic of N-doped oxides. [9,10] It was reported that, N-doped SrTiO 3 show surface N-H band at 1633 cm -1 , nitrite peak at 1453 cm -1 and hyponitrite peak at 1396 cm -1 . So, in NaSPON, AgSPON, and CuSPON, the bands observed around 1630, 1490, and 1330 cm -1 correspond to surface N-H, nitrite, and hyponitrite species, respectively.…”