Journal of Molecular Catalysis A: Chemical 368–369 (2013) 95–106 Contents lists available at SciVerse ScienceDirect Journal of Molecular Catalysis A: Chemical j our na l ho me p age: www.elsevier.com/locate/molcata Study of cupric oxide nanopowders as efficient catalysts for low-temperature CO oxidation D.A. Svintsitskiy a,b , A.P. Chupakhin b , E.M. Slavinskaya a , O.A. Stonkus a , A.I. Stadnichenko a,b , S.V. Koscheev a , A.I. Boronin a,b,∗ a Boreskov Institute of Catalysis SB RAS, Prospect Akademika Lavrentieva 5, Novosibirsk 630090, Russia b Novosibirsk State University, 630090 Pirogova Street 2, Russia a r t i c l e i n f o Article history: Received 12 September 2012 Received in revised form 21 November 2012 Accepted 21 November 2012 Available online 29 November 2012 Keywords: CuO nanoparticles Low-temperature CO oxidation XPS a b s t r a c t CuO nanopowders were prepared by precipitation from alkaline solutions and were studied by TPR- CO + O 2 , XRD, TGA, TPD-He and XPS. All of the precipitated samples were characterized by excellent catalytic properties toward the low-temperature (LT) oxidation of CO with similar T 50 values of 110 ◦ C. In contrast, bulk CuO oxides with sizes greater than 450 nm exhibited no activity at low temperatures. Sev- eral monolayers of chemisorbed species, such as water/hydroxyls and carbonate/hydrocarbonates, were typically observed at the surface of the nanopowders. These species were not critical for the LT oxidation of CO, and their preliminary removal did not substantially change the activity of the nanopowders. XPS results indicated a high deficiency of the oxygen sublattice of the CuO 1-x (x = 0.1–0.15) nanopowders, whereas, for the lattice of bulk CuO, the Cu/O ratio was 1. The highly deficient oxygen sublattice resulted in a disproportionation process, which, in turn, resulted in two observed oxygen forms. An oxygen form with E b (O1s) = 531.3 eV that is highly reactive toward CO was proposed to be responsible for the high catalytic activity of the CuO nanopowders. Slight differences in the Cu2p shake-up satellite structures were observed between the bulk and nanosized samples, which indicated that the electronic structure in the cationic sublattice had changed. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Copper-containing compounds are important subjects of inquiry for various applications: ecology (the solar batteries [1] and gas sensors [2]), electronics (Li-ion batteries [3] and magnetic stor- age [4]), optics (photovoltaic devices [5] and optical switches [6]), materials science (high-temperature superconductors [7]). Differ- ent copper-containing systems in supported [8,9] or unsupported states [10,11] are used in a wide range of relevant heterogeneous catalysis processes: steam methanol reforming [12,13], NO reduc- tion [14,15], CO oxidation [16,17] and PROX [18,19]. The catalytic oxidation of CO has been studied for several decades using various copper-containing catalysts, including copper single crystals [20,21], thin copper oxide films [22,23], oxidized bulk copper [24], copper oxide powders [16,25–29] and supported systems [17,18,30,31]. This interest is supported by the ∗ Corresponding author at: Boreskov Institute of Catalysis SB RAS, Prospect Akademika Lavrentieva 5, Novosibirsk 630090, Russia. Tel.: +7 383 3269631; fax: +7 383 3308056. E-mail address: boronin@catalysis.ru (A.I. Boronin). development of problems in applied heterogeneous catalysis as well as by an understanding of the catalytic activity of copper from a fundamental point of view. Jernigan and Somorjai [22] showed that the activity of copper was influenced by its oxidation state. The CO oxidation activity at 300 ◦ C decreased as copper was further oxidized (Cu > Cu 2 O > CuO). Huang et al. [27] investigated the activity of copper-containing sys- tems in CO oxidation as a function of the number of surface lattice oxygen ions. The best activity was observed for Cu 2 O in comparison with metallic copper and cupric oxide (CuO). The high activity was attributed to metastable non-stoichiometric phases that exhibit the ability to transport surface lattice oxygen. Nagase et al. [28] found that bulk CuO powder was more active in the CO + O 2 oxidation reaction than bulk Cu 2 O powder, whereas CuO prepared by the oxidation of Cu 2 O was less active than the initial Cu 2 O powder. The cumulative data on the catalytic properties of CuO x systems may not allow a definition of which copper state is required to achieve the best activity because numerous factors influence its catalytic properties. The works of Sadykov et al. [29,32] address this prob- lem. The real/defect structure of copper–oxygen systems have to be taken into account during an investigation of catalytic proper- ties. Moreover, the electronic surface structure and the oxidative 1381-1169/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molcata.2012.11.015