Applied Catalysis B: Environmental 132–133 (2013) 423–432 Contents lists available at SciVerse ScienceDirect Applied Catalysis B: Environmental jo ur n al homepage: www.elsevier.com/locate/apcatb Tungsten as an interface agent leading to highly active and stable copper–ceria water gas shift catalyst Anna Kubacka a , Rui Si b , Piotr Michorczyk a,c , Arturo Martínez-Arias a , Wenqian Xu b , Jonathan C. Hanson b , José A. Rodriguez b,∗ , Marcos Fernández-García a,∗∗ a Instituto de Catálisis y Petroleoquímica, CSIC, Campus Cantoblanco, 28049 Madrid, Spain b Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973, USA c Institute of Organic Chemistry and Technology, Cracow University of Technology, Warszawska 24, 31-155 Kraków, Poland a r t i c l e i n f o Article history: Received 25 September 2012 Received in revised form 7 December 2012 Accepted 10 December 2012 Available online xxx Keywords: WGS catalyst Mixed oxides Ceria Copper Tungsten In situ XRD XAFS Vibrational a b s t r a c t A series of W–Cu–Ce mixed oxide catalysts prepared by microemulsion was evaluated in the water-gas shift (WGS) reaction. At low temperatures (<350 ◦ C), the total conversion of CO on the W–Cu–Ce systems was two times larger than on binary Cu–Ce mixed oxides which are well known catalysts for the WGS. In addition and in contrast with Cu–Ce, W–Cu–Ce catalysts were stable and no signs of deactivation were found after 10 h of reaction time. The rationale for the excellent catalytic performance presented by the W–Cu–Ce ternary oxide was elucidated from the viewpoint of a complete structural (e.g. analysis of the long and short range order) and redox behavior characterization using in situ, time-resolved X-ray diffraction (XRD) as well as X-ray absorption (XAS), infrared (diffuse reflectance Fourier transform DRIFTS) and Raman spectroscopies. From a single phase fluorite-type structure, the catalysts show significant structure/redox evolution under reaction conditions as a function of the W and Cu content. As it occurs in the parent Cu–Ce system, the dominant presence of metallic Cu and fluorite-type oxide phases is detected under reaction conditions for the ternary systems. An outstanding promotion of catalytic properties is nevertheless evidenced for samples with W content above 10 at.% and is shown to be related to the presence of oxidized W–Cu local entities. Such local entities, which are obviously characteristic of the ternary system, greatly enhance fluorite redox properties and play an interfacial role between the main metallic Cu and fluorite-type oxide phases. As a consequence of all these effects, incorporation of W into the initial material leads to efficient WGS catalysts, most promising for their application in the so-called low temperature region, e.g. below 350 ◦ C. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Challenges in energy and environmental fields call for the devel- opment of highly active and stable catalysts, allowing for more efficient and cleaner processes [1]. The water gas shift reaction (WGS; CO + H 2 O ↔ H 2 + CO 2 ) has become a leading technology in the chemical industry, particularly in relation to the production of clean hydrogen and energy recovering systems [2]. In this field, alternatives to Cu–ZnO based systems that may work with reason- able stability at low temperatures, e.g. below 350 ◦ C are actively sought. Ceria-based materials have shown rather interesting prop- erties in WGS during recent years, unveiling thus potential to become real alternatives in the future [2,3]. ∗ Corresponding author. ∗∗ Corresponding author. Tel.: +34 915 85 4943; fax: +34 915 85 47 60. E-mail addresses: rodrigez@bnl.gov (J.A. Rodriguez), mfg@icp.csic.es, m.fernandez@icp.csic.es (M. Fernández-García). Cu–CeO 2 systems are among the most active WGS systems and, compared with Pt, Pd, Au and, generally, expensive noble metal based materials, they constitute an interesting alternative from an economical point of view. Among possible different configurations of Cu–CeO 2 materials, Cu–Ce mixed oxides have shown reason- able activity and relatively good stability [4–6]. Due to the different chemical and usually structural properties of doping metals (such as Cu) at Ce-based oxide environments, doping of ceria strongly affects its inherent physico-chemical properties [7]. At a structural level, a dopant can introduce stress into the lattice of an oxide host, inducing in this way the formation of defects to fulfill charge neu- trality and modifying chemical reactivity. On the other hand, the lattice of the oxide host can impose on the dopant element non- typical coordination modes with the subsequent perturbation in the dopant chemical properties. Furthermore, the combination of two metals in an oxide matrix can produce materials with novel structural or electronic properties derived either directly from the chemical state of the doping agent and/or by the corresponding charge neutrality defects that can lead to superior catalytic activity or selectivity [4,5,8–14]. 0926-3373/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apcatb.2012.12.013