Dalton Transactions Dynamic Article Links Cite this: Dalton Trans., 2012, 41, 14381 www.rsc.org/dalton PAPER Aversatile low temperature solid-state synthesis of vanadium nitride (VN) via a “guanidinium-route”: experimental and theoretical studies from the key-intermediate to the final product† Eugenio Furtado de Souza,* a Carlos Alberto Chagas, b Teodorico C. Ramalho c and Ricardo Bicca de Alencastro a Received 19th July 2012, Accepted 13th September 2012 DOI: 10.1039/c2dt31614e An easy and efficient method (“guanidinium route”) to synthesize vanadium nitride (VN) is evaluated in this paper. Initially, ammonium m-vanadate was mixed with guanidinium carbonate, producing an important intermediate, ammonium m-vanadate (GmV), through a solid-state reaction. GmV was decomposed as afunction of the temperature and studied with TGA, DRX, FT-Infrared, Temperature- Programmed Surface Reaction (TPSR) and DFT. We show that GmVis transformed into bulk crystalline VN below 800 °C. XPS, periodic DFT calculations, and elemental analyses show that the surface is not carbon-free. Introduction The insertion of nitrogen and carbon atoms into the crystalline arrays of group IV to VI transition metals produces an interesting class of materials respectively known as interstitial compounds or nitrides and carbides. 1 This class of materials is characterized by “metal–metal” and “metal–nitrogen (carbon)” bonds, proper- ties which confer to it both substantial gains in chemical stability and characteristics specific to both ceramics and metals. Thus, these materials present unique physical and chemical traits, which greatly increase their importance in practical applications and fundamental studies, such as for example, their use as raw materials in cutting tools resistant to wear and corrosion. 2,4 Fur- thermore, since Levy and Boudart, 5 in the 1970s, discovered that tungsten carbide (WC) possesses special catalytic properties, and, from a qualitative point of view electronic properties analo- gous to those of noble metals, the interest in their electronic and magnetic properties 1 has been greatly on the increase. In particular, vanadium nitrides (VN) present magnetic and electronic properties, good thermal and electrical conductivity 1 and important catalytic properties. As an example, it has been applied to n-butane dehydrogenation and NH 3 synthesis and decomposition, 6,7 and it has shown high activity in hydrogen- ation, hydrogenolysis, hydrodesulfurization (HDS) and hydro- denitrogenation of hydrocarbons. 8 Furthermore, VN has recently also been used as an important and promising material for elec- trodes for supercapacitors. 9 However, despite its many qualities, the synthesis of VN is usually difficult, requiring elevated temp- eratures and long reaction times. Conventionally, they are pre- pared by different and complex methods which include self- propagating high temperature synthesis (SHS), 10 nitridation via the urea pathway, 11,12 chemical vapor deposition, 13 reduction– nitridation reactions, 14 reaction of vanadium metallic with nitro- gen, 1 carbothermal reduction and nitridation of vanadium oxides in N 2 , 15 and temperature programmed reactions. 16–21 The search for a more general, inexpensive, safe and efficient methodology to produce new classes of materials is highly desired and attempted by materials chemists, physicists and engineers. As may be seen in the literature, methods to produce a variety of nitrides and carbides are already known. 3 In the case of interstitial compounds, Sherif 22 has proposed a novel pro- cedure to prepare tungsten carbide through the solid-state reac- tion between tungsten hexachloride and guanidinium hydrochloride at temperatures below 800 °C. However, despite its promising results, experimental and theoretical studies on this methodology are relatively scarce. In the present paper, we report our experimental and theoretical results on the totally solid-state synthesis of the VN at low temperatures, through a simple, safe and innovative method. Initially, VN was prepared via the solid- state reaction of guanidinium carbonate and ammonium m-vana- date, forming a key-intermediate whose chemical structure and local properties were studied by means of DFT methods. More- over, in order to acquire some indication on the factors playing a † Electronic supplementary information (ESI) available: XPS spectra of the V2p3/2(A), N1s(B), O1s(C) and C1s(D) regions for the samples pre- pared at 300 °C and 400 °C. See DOI: 10.1039/c2dt31614e a Laboratorio de Modelagem Molecular-LABMMOL, Instituto de Química, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos No 149, CT, Bloco A, sala 609, 21941-909 - Rio de Janeiro-RJ. E-mail: eugeniofs@iq.ufrj.br; Fax: (21) 2562-7132; Tel: (21) 2562-7132 b Núcleo de Catálise, Programa de Engenharia Química, COPPE, Universidade Federal do Rio de Janeiro, Av. Horácio Macedo, No 2030, CT - Bloco G, sala G-115, 21941-914 - Rio de Janeiro, RJ. Fax: (21) 25628300; Tel: (21) 25628304 c Departamento de Química, Universidade Federal de Lavras, UFLA, Campus Universitário - UFLA- Cx. postal 3037, 37200-000 - Lavras, MG. Fax: (35) 38291271; Tel: (35) 38291552 This journal is © The Royal Society of Chemistry 2012 Dalton Trans., 2012, 41, 14381–14390 | 14381 Downloaded by University of California - San Diego on 07 January 2013 Published on 14 September 2012 on http://pubs.rsc.org | doi:10.1039/C2DT31614E View Article Online / Journal Homepage / Table of Contents for this issue