Short Communication Understanding on the origins of hydroxyapatite stabilized gold nanoparticles as high-efficiency catalysts for formaldehyde and benzene oxidation Yu Wang a,b , Bing-bing Chen a,b , Mark Crocker c , Yu-jing Zhang a,b , Xiao-bing Zhu b , Chuan Shi a,b, ⁎ a Key laboratory of Industrial Ecology and Environmental Engineering (MOE), Dalian University of Technology, Dalian, People's Republic of China b Laboratory of Plasma Physical Chemistry, Dalian University of Technology, Dalian, People's Republic of China c Center for Applied Energy Research, University of Kentucky, Lexington, KY 40511, USA abstract article info Article history: Received 1 August 2014 Received in revised form 21 October 2014 Accepted 28 October 2014 Available online 3 November 2014 Keywords: Hydroxyapatite Sintering-resistance Supported gold catalysts VOC oxidation Cerium oxide Hydroxyapatite as a green and abundant material was found to enhance the stabilization of gold nanoparticles against sintering. The origins of such stabilization of HAP on supported gold nanoparticles were investigated in the present study. Phosphate groups interacted and stabilized nano-gold at lower temperature (≤400 °C), while hydroxyl group contributed to the stabilization at higher temperature (≤600 °C). Both of them contribut- ed to the strong sintering-resistant for calcination as high as 600 °C. For the first time we found that Au/HAP and Au/CeO 2 /HAP catalysts are highly active and stable for formaldehyde and benzene oxidation. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Supported gold catalysts have attracted tremendous attention owing to the pioneering discovery by Haruta [1]. The last decade has witnessed a rapid growth of interest in the catalytic properties of gold, a variety of oxide-supported Au catalysts, such as Au/CeO 2 [2], Au/TiO 2 [3], Au/Fe 2 O 3 [4], Au/ZrO 2 [5], and Au/Al 2 O 3 [6] catalysts have been reported. Despite the many potential applications of supported gold catalysts, one of the most important limitations in the use of gold catalysts is their sintering of gold nanoparticles at high temperatures. Certain applica- tions would require the catalyst to survive and remain effective at high temperature and for long times. It is well established that catalytic activity and stability of supported gold depend strongly on the choice of the supports and the specific interaction between gold and the support [7]. Recently, hydroxyapatite (HAP, Ca 10 (PO 4 ) 6 (OH) 2 ) has attracted inter- est for use in a variety of applications. Notably, the use of HAP as a support for nano-gold was reported to perform excellent CO oxidation activity and enhance the stability of gold nanoparticles against sintering at tem- peratures as high as 600 °C [8,9]. Although the origin of this stabilization has to date been little studied, it has been ascribed to the presence of PO 4 3- and OH - groups [10]. The excellent sintering - resistant property of this catalyst provides a new opportunity for the development of stable nano-gold catalysts. The present work is devoted to the understanding of the essential fea- tures of the catalysis of the gold nanoparticles loaded HAP (Au/HAP) in formaldehyde (HCHO) and benzene (C 6 H 6 ) oxidation. In this work, we first compare Au/CeO 2 and Au/HAP catalysts to confirm the stabilizing ef- fect of the HAP support; subsequently, we compare Au/HAP and Au/FAP (fluorapatite, Ca 10 (PO 4 ) 6 F 2 ) catalysts, the latter containing only PO 4 3- groups, to distinguish the stabilizing effect of PO 4 3- and OH - groups. It is found that surface hydroxyls and phosphate groups followed an inter- esting regularity to stabilize the gold nanoparticles from growing up for calcination, and for the first time, HAP supported Au catalyst is reported to be very active for HCHO and benzene oxidation, even in the presence of moisture. 2. Experimental 2.1. Catalyst preparation Three kinds of supports of HAP, FAP and CeO 2 /HAP were synthesized by a chemical precipitation method. Gold nanoparticles were loaded on the supports by a deposition–precipitation method targeting at 1 wt.% Au loadings. Details were described in the Supplementary data. Catalysis Communications 59 (2015) 195–200 ⁎ Corresponding author at: Key laboratory of Industrial Ecology and Environmental Engineering (MOE), Dalian University of Technology, Dalian, People's Republic of China. Tel.: +86 411 84986083. E-mail address: chuanshi@dlut.edu.cn (C. Shi). http://dx.doi.org/10.1016/j.catcom.2014.10.028 1566-7367/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Catalysis Communications journal homepage: www.elsevier.com/locate/catcom