Review Chemistry Graphene-supported platinum catalysts for fuel cells Nedjeljko Seselj • Christian Engelbrekt • Jingdong Zhang Received: 5 November 2014 / Accepted: 25 December 2014 Ó Science China Press and Springer-Verlag Berlin Heidelberg 2015 Abstract Increasing concerns with non-renewable energy sources drive research and development of sustainable energy technology. Fuel cells have become a central part in solving challenges associated with energy conversion. This review summarizes recent development of catalysts used for fuel cells over the past 15 years. It is focused on polymer electrolyte membrane fuel cells as an environmentally benign and feasible energy source. Graphene is used as a promising support material for Pt catalysts. It ensures high catalyst loading, good electro- catalysis and stability. Attention has been drawn to structural sensitivity of the catalysts, as well as polymetallic and nanos- tructured catalysts in order to improve the oxygen reduction reaction. Characterization methods including electrochemical, microscopic and spectroscopic techniques are summarized with an overview of the latest technological advances in the field. Future perspective is given in a form of Pt-free catalysts, such as microbial fuel cells for long-term development. Keywords Fuel cells  Graphene  Platinum  Oxygen reduction reaction (ORR)  Electrocatalysis  Energy conversion 1 Introduction Due to depleting fossil fuel resources accompanied with drastic climate changes, looking for renewable and sus- tainable energy is imminent. Fuel cell technology is among many approaches recently developed aiming at solving the global energy challenges. Fuel cells (FCs) are electro- chemical devices that convert chemical energy stored in fuel molecules into electric energy via electrochemical reactions [1]. Basic elements in a fuel cell are cathode, anode, electrolyte and fuels such as hydrogen, methanol, ethanol and formic acid [2]. Critical catalyzed reactions occur at both electrodes. As an example, reactions for a direct methanol fuel cell are [3]: Cathode: 1 = 2 O 2 þ 2H þ þ 2e  ! H 2 O Anode: CH 3 OH þ H 2 O ! 6H þ þ 6e  þ CO 2 FCs provide clean energy with low pollution. Several different types of fuel cells have been developed and categorized according to fuels and electrolytes. Important technologies include hydrogen FCs such as alkaline fuel cell (AFC), polymer electrolyte membrane fuel cell (PEMFC), phosphoric acid fuel cell (PAFC), solid oxide fuel cell (SOFC) and hydrocarbon FCs, which include direct methanol fuel cell (DMFC), direct ethanol fuel cell (DEFC) and direct formic acid fuel cell (DFAFC) [1, 4–7]. Different fuel cell technologies with potential application are summarized in Fig. 1 and Table 1. In this work, we focus on hydrocarbon FCs, in which liquid hydrocarbons, such as methanol or ethanol, are fuels and polymer electrolyte membrane (PEM, primarily NafionÒ) the electrolyte. The PEM separates electrodes and acts as a proton conductor. Pt-based materials are commonly used as catalysts with appealing properties such as low operating temperatures, high power densities and relative ease of scale-up. However, certain challenges are yet to be overcome. The main limiting issue for PEM fuel cells is the use of Pt, an expensive metal [9]. Poisoning is also a concern for Pt catalysts. Only a few parts per billion of CO 2 Electronic supplementary material The online version of this article (doi:10.1007/s11434-015-0745-8) contains supplementary material, which is available to authorized users. N. Seselj  C. Engelbrekt  J. Zhang (&) Department of Chemistry, Technical University of Denmark, 2800 Lyngby, Denmark e-mail: jz@kemi.dtu.dk 123 Sci. Bull. www.scibull.com DOI 10.1007/s11434-015-0745-8 www.springer.com/scp