Applied Catalysis B: Environmental 182 (2016) 1–14 Contents lists available at ScienceDirect Applied Catalysis B: Environmental journal homepage: www.elsevier.com/locate/apcatb Effect of Cu additives on the performance of a cobalt substituted ceria (Ce 0.90 Co 0.10 O 2– ) catalyst in total and preferential CO oxidation Thandanani Cwele, N. Mahadevaiah, Sooboo Singh, Holger B. Friedrich ∗ Catalysis Research Group, School of Chemistry and Physics, University of KwaZulu-Natal, Westville Campus, Durban 4000, South Africa a r t i c l e i n f o Article history: Received 9 April 2015 Received in revised form 26 August 2015 Accepted 27 August 2015 Available online 29 August 2015 Keywords: CO–PROX CO oxidation Ceria Solid-solution Cu–Co-containing catalysts a b s t r a c t The study reports the modification of the developed Ce 0.90 Co 0.10 O 2– catalyst by incorporating copper ions in order to improve the catalytic activity for total and preferential CO oxidation (TOX and PROX). A series of metal ion substituted ceria catalysts, Ce 0.90 Co 0.10 O 2– and Ce 0.90-x Cu x Co 0.10 O 2– (x = 0.01, 0.03 and 0.05) were synthesized in a single step by the urea-assisted solution combustion method. The compositions, textural and structural properties of the catalysts were characterized by XRD, XPS, Raman, H 2 -TPR and ICP-OES. The insertion of Cu ions in Ce 0.90 Co 0.10 O 2– greatly enhanced the reducibility and improved the activity, with especially the Ce 0.85 Cu 0.05 Co 0.10 O 2– catalyst showing superior catalytic performance compared to other bimetallic catalysts. Analysis of the reaction profiles and rate calculations suggest that H 2 and CO oxidation over Ce 0.90 Co 0.10 O 2– may be occurring on the same active sites, while the two reactions appear to be taking place on independent sites over the Cu-containing catalysts. In addition, the effect of H 2 O/CO 2 in PROX has been studied. The degree of deactivation by H 2 O and CO 2 decreased with increasing the Cu content in the catalysts. The presented catalysts are highly active, selective and stable in TOX and PROX. © 2015 Elsevier B.V. All rights reserved. 1. Introduction In the context of growing environmental concerns and inter- est in the development of clean energy alternative technologies, polymer electrolyte membrane fuel cells (PEMFCs) have become an important subject of research aimed at addressing energy-related concerns. This is due to their low temperature of operation, rea- sonably high power density and zero emission of pollutants [1]. Most of the hydrogen required as fuel for PEMFCs is produced by steam reforming of hydrocarbon fuels, followed by the water gas shift (WGS) reaction, in order to improve hydrogen yield. The hydrogen produced after this step co-exists with ca.1% of carbon monoxide (CO) and other gaseous products [2]. This amount of CO in the hydrogen stream drastically decreases the efficiency of the Pt anode catalyst in converting hydrogen fuel to energy [3,4]. There- fore, the removal of CO from the reformate gas is necessary in order to ensure maximum PEMFC power output. To date, CO preferential oxidation is one of the most effective ways for the purification of the reformate stream, with minimal hydrogen consumption [5]. Different types of catalyst formulations have been explored and studied for the total CO oxidation (TOX) and preferential CO ∗ Corresponding author. Fax: +27 31 2603091. E-mail address: friedric@ukzn.ac.za (H.B. Friedrich). oxidation (PROX) [6,7]. Among other transition metals, platinum group metal (PGM) based catalysts have been widely studied and applied for PROX. As early as the 1960s, Pt/Al 2 O 3 catalysts were used by the Engelhard Corperation in hydrogen plants to remove CO prior to ammonia synthesis [8]. Since then, more catalysts have been developed to purify hydrogen for PEMFC applications. The most studied PGMs are Pt and Pd and to a lesser extent Rh and Ru, supported on materials such as silica, alumina, zeolites and ceria [9]. Ceria-based materials are well known for their applications as oxygen storage materials in automotive three-way catalytic con- verters (TWC), also these catalysts have gained recognition in a wide range of applications, most notably in solid oxide fuel cells, low-temperature WGS and CO oxidation reactions [10,11]. The cat- alytic behaviour demonstrated by ceria-based materials is often attributed to their good ionic conduction, temperature stability and the facile redox cycle between Ce 3+ and Ce 4+ [12]. Total CO oxida- tion and preferential CO oxidation have received more attention over these materials due to their applications in emission control and fuel cell technologies [13–15]. In most cases, ceria has been used as a support for active precious metals, such as Pt, Au or Pd [15–17]. Despite good CO oxidation activity shown by these cata- lysts, the drawback is that they are also active for the undesirable H 2 oxidation reaction. http://dx.doi.org/10.1016/j.apcatb.2015.08.043 0926-3373/© 2015 Elsevier B.V. All rights reserved.