H2 evolution on Lanthanum and Carbon co-doped NaTaO3 Photocatalyst

Available online at BCREC Website: http://bcrec.undip.ac.id Bulletin of Chemical Reaction Engineering & Catalysis, 9 (2), 2014, 81-86 Research Article H2 Evolution on Lanthanum and Carbon Co-doped NaTaO3 Photocatalyst Husni Husin 1*, M. Mahidin 1, Z. Zuhra 1, Fikri Hafita 2 1 Department of Chemical Engineering, Syiah Kuala University, Jl. Tgk. Syeh Abdurrauf No. 7, Kampus Darussalam, Banda Aceh 23111, Indonesia 2 Department of Chemical Engineering, Malikussaleh University, Lhoekseumawe, Aceh Utara 24300, Indonesia Received: 28th September 2013; Revised: 16th February 2014; Accepted: 28th February 2014 Abstract We report a carbon-modify lanthanum doped sodium tantalum oxide powders (La-C-NaTaO3) by sol-gel process. The resultant materials are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The X-ray diffraction of La-CNaTaO3 show a single phases with a good crystallinity and without any impurity. The sample is exactly indexed as NaTaO3 monoclinic structure with the space group P2/m. The SEM measurements give a smaller particle size of doped NaTaO3 than pure NaTaO3. The effect of dopant on the photocatalytic activity of La-C-NaTaO3 in the photocatalytic of hydrogen generation is studied and compared with pure NaTaO3. The results show that the rate of hydrogen evolution over La-C-NaTaO3 is higher as compared to that of pure NaTaO3. The enhancement of photocatalytic activity of La-C-NaTaO3 nanocrystalline is mainly due to their capability for reducing the electron hole pair recombination. The La-C-dopant is believed to play a key role in the enhancement of photocatalytic properties of La-CNaTaO3 crystalline. © 2014 BCREC UNDIP. All rights reserved Keywords: Photocatalyst; La-C-doped; sodium tantalum oxide; hydrogen generation How to Cite: Husin, H., Mahidin, M., Zuhra, Z., Hafita, F. (2014). H2 evolution on Lanthanum and Carbon co-doped NaTaO3 Photocatalyst . Bulletin of Chemical Reaction Engineering & Catalysis, 9 (2): 81-86. (doi:10.9767/bcrec.9.2.5530.81-86) Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.2.5530.81-86 1. Introduction Hydrogen has emerged as a potential energy carrier in various low greenhouse gas energy applications due to its renewability and environmentally friendly [1-4]. Photocatalytic water splitting into hydrogen using solar energy, as one of the most promising ways to obtain hydrogen and has attracted great scientific interest [5-6]. Much attention has been paid to find* Corresponding Author. E-mail: (H. Husin) Tel.: +62-65-17412301; fax: +626517552222 ing ways to produce hydrogen from renewable energy sources such as the sun and wind [7]. Hydrogen production from water by using semiconductors as photocatalysts provides a potential way to obtain hydrogen efficiently, due to its clean, low-cost and environmentally friendly production process by utilizing solar energy. Sodium tantalum oxide has been proved to be a promising photocatalyst material for applications in hydrogen production. Doping rareearth or other metal oxides into the perovskite type alkali tantalates can increase their capability of trapping and transferring electron/hole bcrec_5530_2014 Copyright © 2014, BCREC, ISSN 1978-2993 Bulletin of Chemical Reaction Engineering & Catalysis, 9 (2), 2014, 82 pairs, which improves their photocatalytic activities [8-9]. Husin et al. [10] observed that the water-splitting reaction of NaTaO3 could be improved by lanthanum doping, because the Ladoped NaTaO3 powders have a small particle size with high crystallinity. But this photocatalyst works only under UV-light irradiation. Zhou et al. reported that Fe-doped NaTaO3 was red-shifted to the visible region, which potentially could be active for overall water splitting under visible light irradiation [11]. Recently, Fu et al. synthesized N-doped NaTaO3 photocatalysts, which showed high photo activity for formaldehyde photo-degradation under visible-light irradiation [12]. However, in their studies, they did not use this photocatalyst to split water. In semiconductor doping technology, co-doping can overcome some limitations of single ion doping, such as poor thermal stability and more recombination centres for electron-hole pairs. Thus, we attempt to dope carbon at La-NaTaO3 to modify its performance. To our knowledge, studies on carbon doping at La-doped NaTaO3 and its photocatalytic performance have not been reported so far. In this work, a La-C co-doped NaTaO3 photocatalyst was synthesized by the sol-gel reaction method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The hydrogen evolution was used to evaluate the photocatalytic properties of the photocatalyst. The effect of various carbon contain will be report in the future work. 2. Materials and Methods 2.1. Materials All reagents were of analytical grade and were used without further purification. Commercially available tantalum chloride (TaCl5) (Acros, 99.9%), ethanol (Acros, 99.5%), La(NO3)3.6H2O (Merck, purity: 98.0%), NaOH (Acros, ACS grade), methanol (Acros, 99.9% HPLC grade), and sucrose (Fisher scientific), citric acid (across, 99.0%), NH3 (35% Fisher Scientific) were used as received. Tantalum was prepared using ethanol. Other solutions were dissolved using high purity deionized water. 2.2 Catalyst Preparation La-C-doped NaTaO3 was synthesized by means of sol-gel procedure using ethanol as solvent system. All chemicals were analytical grade reagents and used without further purification. In a typical procedure, a TaCl5 was firstly dissolved in ethanol solution and then NaOH dissolved in deionized water. La(NO3)3.6H2O was dissolved in deionized water and then added into the solution. The mixture was mixed with C12H22O11 solution for 2 h under magnetic stirring. Citric acid solution was employed as a chelating agent in the developed process. Under vigorous stirring, 50 ml of citric acid solution was slowly dropped into the above solution to produce sol solution. The pH was adjusted to 4 with NH3 solution. Then, a La-C-doped NaTaO3 compound was obtained by heating the mixture at constant temperature of 80 oC until a white gels formed. The obtained gel was dried in oven at 100 oC. The resulting powder precursor was sintered at 400 oC and continuous heating at 800 oC for 8 h under air flow. The sample was cooled to room temperature and underwent characterization. In this work, we also prepared the NaTaO3 sample without doping for comparison. 2.2. Catalyst Characterization To investigate the morphology of the structure, a scanning electron microscope (SEM) images of the final nanosized of the La-C-NaTaO3 was recorded by a (SEM, Philips XL-30) apparatus. The transmission electron microscope (TEM) images of the nanosized NaTaO3 were recorded by a Philips/FEI Tecnai 20G2 S-Twin TEM apparatus. The samples were characterized by X-ray powder diffraction (XRD). Th (...truncated)