Synthesis and characterization of ZnO(1-x)Nx by a novel method and its potential application as photocatalyst. Thermochemical Processes Group, IMDEA Energy

1. In summary, “Solution Combustion Method” has been used for preparing ZnO particles doped with nitrogen as it is suggested by the Raman spectra. This fact could indicate that nitrogen has been successfully introduced to the crystalline lattice creating a new absorption band in the visible range and therefore decreasing the bandgap. Raman spectra has also verified that the highest amount of nitrogen included into the crystal lattice of the catalyst are shown generally in the catalysts prepared with the lowest ratio (Urea-Zinc Nitrate Hexahydrate) and calcination temperature. As further work, test of catalytic activity will be performed in the photocatalytic reaction system displayed in above. Julio Núñez Casas , Víctor A. de la Peña O’Shea, Juan M. Coronado, David Serrano Granados Thermochemical Processes Group, IMDEA Energy, c/Tulipán, s/n, E-28933 Móstoles (Madrid), Spain * email:julio.nunez@imdea.org Synthesis and characterization of ZnO (1-x) N x by a novel method and its potential application as photocatalyst Morphological characterization by ESEM depicts agglomerates of micrometer-sized crystals for ZnNU1 catalysts serie with triangular and hexagonal-prism-shaped crystals with an edge average of 2-4 μm. The crystals show high uniformity and low surface defects. [4] For the groups ZnNU2 and ZnNU3 agglomerates without specific particle morphology were observed. This fact is attributed to the increasing exothermicity of the combustion reaction leading to smaller crystal size than for ZnNU1 group. The XRD patterns of all of the catalysts prepared can be indexed as the wurtzite structure, showing minor differences with respect to the XRD pattern of ZnO Greenhouse gases such as CO 2 are the primary cause of global warming. One of the most promising and challenging routes for the remediation of this problem is the valorization of CO 2 by its photoreduction with water under sunlight radiation to obtain chemicals with potential applications as fuels. This kind of process requires semiconductor materials such as TiO 2 and ZnO in order to separate the electron and the holes generated during the photoexcitation of the materials under a suitable wavelenght that will perform the photoreduction of CO 2. ZnO has been widely used as a photocatalyst, due to its high activity, lowcost and environmentally friendly properties. [1] However, the main disadvantage is that the photocatalytic activity of ZnO is limited to wavelengths in the UV region. Consequently , in order to use this photocatalyst under visible light is necessary to modify its optical absorption properties. A successful approach is to introduce non-metallic elements in the crystalline lattice of this material in order to reduce the band gap energy. [2] Doping of ZnO with N has been performed by mean of a facile procedure called “Solution Combustion Method”. INTRODUCTION EXPERIMENTAL PROCEDURE RESULTS AND DISCUSSION 1. N. Sobana, M. Swaminathan, Sep. Purif. Technol. 56 (2007) 101–107 2. M. Aresta and A. Dibenedetto, Dalton Transactions 28 (2007) 2975-2992 3. V. Houskova, V. Stengl, S. Bakardjieva, F. Oplustil, J. Phys. Chem. A. 111 (2007) 4215–4221. 4. X. Zhou, Z. Xie, Z. Jiang, Q. Kuang, and L. Zheng, Chem. Commun., (2005) 5572–5574. 5. A. Kaschner, U. Haboeck, M. Strassburg, M. Strassburg, G. Kacz-marczyk, A. Hoffmann, C. Thomsen, Appl. Phys. Lett. 80 (11) (2002) 1909– 1911 Acknowledgments References CONCLUSION Synthesis procedure: Solution Combustion Method Table of the catalysts prepared Further work: test catalyst activity in a photoreactor Raman spectra of all the catalysts shows a sharp and strong peak observed at 437 cm-1 and two more peaks at 380 cm-1 and 415 cm-1 associated with the ZnO-wurtzite phase. Additional peaks with respect to pure ZnO are observed at 270, 507, 582, and 642 cm-1, that are attributed to the Zn-N stretching.[5]. UV-Vis spectrums of all the catalysts show a new absorption band between 450-600 nm reaching a maximum around 500 nm. When ratio Urea/Zn increases absortivity intensity decreases. Calculated bandgaps of the catalysts from absortivity show a general decrease respect to pure ZnO (3.3 eV) ENE-2009-09432