Highly alloyed PtRu black electrocatalysts for methanol oxidation prepared using magnesia nanoparticles as sacrificial templates Liangliang Zou a, b , Jing Guo a , Juanying Liu a , Zhiqing Zou a , Daniel L. Akins c , Hui Yang a, * a Shanghai Advanced Research Institute, Chinese Academy of Sciences (CAS), Shanghai 201210, China b University of the CAS, Beijing 100039, China c CASI and the Chemistry Department of The City College of New York, CUNY,10031, USA highlights  Magnesia is used as a sacrificial support for the synthesis of PtRu black catalyst.  The PtRu black electrocatalysts show high alloying degree and small particle size.  Catalytic activity for MeOH oxidation is ca. twice that of commercial PtRu black.  In-house PtRu black catalysts have enhanced durability over commercial catalysts. article info Article history: Received 28 July 2013 Received in revised form 16 September 2013 Accepted 18 September 2013 Available online 30 September 2013 Keywords: Platinumeruthenium black Alloying Methanol oxidation Direct methanol fuel cell abstract Synthesis of small particle size, highly alloyed PtRu black catalysts for application in direct methanol fuel cells remains a substantial challenge. In this work, PtRu (1:1) black catalysts have been synthesized using Pt carbonyl complex and RuCl 3 as initial precursors and magnesia nanoparticles as sacrificial templates. Magnesia is used to prevent the aggregation of synthesized PtRu nanoparticles during heat treatment, and thus promoting the controllable formation of PtRu black of high alloy composition and small particle size. X-ray diffraction shows that the PtRu black nanoparticles have a single-phase face-centered cubic structure and that the degree of alloying increases with treatment temperature. The mean particle size of the PtRu black catalysts, after heat-treatment from 250 to 300  C, is found to be ca. 3 nm, only slightly larger than that of commercial Johnson-Matthey PtRu black, but more highly alloyed. Electrochemical measurements indicate that the catalytic activity for methanol oxidation on in-house prepared PtRu black catalysts is about twice that of the commercial product, with greater durability, indicating that the degree of alloying between Pt and Ru plays an important role in improving both catalytic activity and durability of the catalysts when used for methanol oxidation. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction PtRu-based catalysts are regarded generally as the most suitable anode catalysts for direct methanol fuel cells (DMFCs) because they can completely oxidize methanol to CO 2 via a rapid, two-step mechanism. This mechanism involves (CO) ad on the Pt site react- ing with (OH) ad on a neighboring Ru site. The electrocatalytic ac- tivity is therefore strongly dependent on the distribution of Pt and Ru sites at the atomic level [1,2]. Until recently, much effort has been devoted to the synthesis of bimetallic PtRu nanoparticles on various supports such as carbon materials [3e5], metal oxide modified carbon materials [6] and transition metal oxides [7,8]; with the best Pt:Ru ratio typically reported to be 1:1. However, for practical applications, it is highly desirable to reduce the thickness of the catalytic layer to improve mass transportation and to decrease the inner electrical resistance. As a result, PtRu catalysts with high metal loading or even unsupported PtRu black have been extensively used in the DMFCs [9,10]. However, synthesis of PtRu black catalysts of higher catalytic activity, greater alloy percentage, with more uniform nanoparticle size distribution, and not requiring a support remains an enormous challenge. There are only a few reports that focus on the synthesis of PtRu black catalyst, likely due to the conflict of the desired small particle size and high alloy composition. Moreover, there are only a few reports in the literature dealing with the important role that alloy extent plays in the electrocatalytic activity and stability of PtRu * Corresponding author. Fax: þ86 21 20325112. E-mail addresses: yangh@sari.ac.cn, huiyang65@hotmail.com (H. Yang). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour 0378-7753/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jpowsour.2013.09.086 Journal of Power Sources 248 (2014) 356e362