Short Communication Complete oxidation of formaldehyde at ambient temperature over γ-Al 2 O 3 supported Au catalyst Bing-bing Chen a,b , Xiao-bing Zhu b , Mark Crocker c , Yu Wang a,b , Chuan Shi a,b, ⁎ a Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), Dalian University of Technology, Dalian, PR China b Laboratory of Plasma Physical Chemistry, Dalian University of Technology, Dalian, PR China c Center for Applied Energy Research, University of Kentucky, Lexington, KY 40511, USA abstract article info Article history: Received 30 May 2013 Received in revised form 8 August 2013 Accepted 13 August 2013 Available online 22 August 2013 Keywords: Formaldehyde Catalytic oxidation Au/γ-Al 2 O 3 Room temperature Au supported on γ-Al 2 O 3 prepared by deposition–precipitation (DP) using urea is found to be a highly active catalyst for the total oxidation of HCHO at room temperature under humid air, without the need for a reducible oxide as support. In-situ DRIFTS studies suggested that the surface hydroxyl groups played a key role in the partial oxidation of HCHO into the formate intermediates, which can be further oxidized into CO 2 and H 2 O with partic- ipation of nano-Au. This study challenges the traditional idea of supporting noble metals on reducible oxides for HCHO oxidation at room temperature. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Given that formaldehyde is a major indoor air pollutant, significant efforts have been directed at indoor HCHO removal to meet environ- mental regulations and human health needs [1,2]. Catalytic oxidation is recognized as the most promising HCHO removal technology. Indeed, supported Pt catalysts such as Pt/TiO 2 and Pt/MnOx–CeO 2 have been shown to be active for HCHO complete oxidation at room temperature [3–6]. Moreover, in our previous study, 1% Au/CeO 2 catalyst was found to provide 100% HCHO conversion at room temperature (RT). It was suggested that HCHO was partially oxidized into [HCOO] s intermediates on the support, further oxidation of these intermediates required the participation of gas phase oxygen activated by Au nanoparticles [7]. In general, reducible oxides have been used as the support of choice in past studies because of their high concentrations of oxygen defects and their ability to stabilize high dispersions of Pt or Au. With HCHO oxidation aside, γ-Al 2 O 3 is the most common support material for metal catalysts, due to its low cost, thermal and chemical stability, high surface area and amphoteric character [8,9]. However, γ-Al 2 O 3 is considered to be a poor support for low temperature HCHO oxidation catalysts due to its irreducibility [10]. It is generally agreed that a reducible oxide such as ceria has strong surface interactions with the supported metal which help to stabilize the latter. Such inter- action might cause the charge transfer from the supported metal to the support, which leads to the weakened bond of the support, such as Ce\O bond [7,11,12]. That is the way that the surface oxygen species become very active and normally believed to have key roles in low temperature HCHO oxidation [13–15]. Herein, we report for the first time that γ-Al 2 O 3 supported Au is a very active catalyst for HCHO oxidation at RT even in the presence of moisture. It is found that although there is no active surface oxygen on γ-Al 2 O 3 , surface hydroxyls have the ability to partially oxidize HCHO into formate intermediates, which can be further oxidized into CO 2 and H 2 O by nano-Au. This study challenges the traditional idea of supporting noble metals on reducible oxides for HCHO oxidation at RT. 2. Experimental section 2.1. Catalyst preparation Au/γ-Al 2 O 3 catalysts with nominal gold loadings of 0.25, 0.5 and 1 wt.% were prepared by the deposition–precipitation method, using urea as precipitant, according to a literature procedure [7]. The support- ed gold catalysts were dried in air at 80 °C for 16 h, and calcined in air at 200 °C for 4 h. 2.2. Catalyst characterization The catalysts were characterized by CO-chemisorption, UV–vis spectra, transmission electron microscopy (TEM), H 2 temperature- programmed reduction (H 2 -TPR), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The detailed procedures used are described in the Supplementary data. Catalysis Communications 42 (2013) 93–97 ⁎ Corresponding author at: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), Dalian University of Technology, Dalian, PR China. Tel.: +86 411 84986083. E-mail address: chuanshi@dlut.edu.cn (C. Shi). 1566-7367/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.catcom.2013.08.008 Contents lists available at ScienceDirect Catalysis Communications journal homepage: www.elsevier.com/locate/catcom