Journal of Power Sources 196 (2011) 7594–7600 Contents lists available at ScienceDirect Journal of Power Sources jou rnal h omepa g e: www.elsevier.com/locate/jpowsour Electrochemical and fuel cell evaluation of Co based catalyst for oxygen reduction in anion exchange polymer membrane fuel cells M. Mamlouk a,∗ , S.M. Senthil Kumar a , Pascal Gouerec b , Keith Scott a a School of Chemical Engineering and Advanced Materials, Merz Court, University of Newcastle, Newcastle upon Tyne NE1 7RU, United Kingdom b GPMaterials, Le Mirabeau, 11 bd Chantemerle, Aix les Bains 73100, France a r t i c l e i n f o Article history: Received 2 February 2011 Received in revised form 19 April 2011 Accepted 20 April 2011 Available online 28 April 2011 Keywords: Alkaline membrane fuel cell Anion exchange Cobalt Oxygen reduction Non precious metal catalysts a b s t r a c t Co based catalyst were evaluated for oxygen reduction (ORR) in liquid KOH and alkaline anion exchange membrane fuel cells (AAEMFCs). In liquid KOH solution the catalyst exhibited good performance with an onset potential 120 mV more negative than platinum and a Tafel slope of ca. 120 mV dec -1 . The hydrogen peroxide generated, increased from 5 to 50% as the electrode potential decreased from 175 to -300 mV vs. SHE. In an AAEMFC environment, one catalyst (GP2) showed promising performance for ORR, i.e. at 50 mA cm -2 the differences in cell potential between the stable performance for platinum (more pos- itive) and cobalt cathodes with air and oxygen, were only 45 and 67 mV respectively. The second catalyst (GP4) achieved the same stable power density as with platinum, of 200 and 145 mW cm -2 , with air at 1 bar (gauge) pressure and air (atm) cathode feed (60 ◦ C), respectively. However the efficiency was lower (i.e. cell voltage was lower) i.e. 40% in comparison to platinum 47.5%. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Solid (cation-free) OH - ion conducting polymer alkaline elec- trolyte membranes (AEM) could hold the key answer to many of the limitations of polymer electrolyte membrane fuel cell (PEMFC). AEMs exhibit several advantages over PEMFCs including: the oxy- gen reduction reaction (ORR) is faster under alkaline conditions than in acidic conditions therefore providing lower activation losses [1], non-precious metal catalysts (NPMCs) can be used quite effectively [2], increased number of cheap materials for cell com- ponents due to less corrosive environment [3]. Other major issues with PEMFCs of water management, cross-over and cathode flood- ing are potentially addressed in AEMFCs by water and ion transport away from the cathode to the anode mitigating crossover and flood- ing problems [4]. AEMs are solid polymer electrolyte membranes that contain positive ionic groups (e.g., quaternary ammonium (QA) func- tional groups such as poly–N + CH 3 ) and mobile negatively charged anions (e.g., usually OH - ). Several types of anion exchange mem- branes based on quaternary ammonium groups were reported in the literature, radiation-grafted PVDF, ETFT, and FEP polymers containing vinylbenzyl chloride (VBC) units [5–7], quaternized poly(ether sulfone) PES [8–10], quaternized poly(2,6-dimethyl-1,4- phenylene oxide) PPO [11], quaternized poly(phthalazinone ether ∗ Corresponding author. Tel.: +44 191 222 5207; fax: +44 191 222 5292. E-mail address: mohamed.mamlouk@ncl.ac.uk (M. Mamlouk). sulfone ketone) PPESK [12], quaternized poly(phenylene) [13,14] and quaternized copolymer of poly(methyl methacrylate-co-butyl acrylate-co-vinylbenzyl chloride) [15]. There are several well-known chemistries and classes of non- precious cobalt catalyst materials for the oxygen reduction reaction (ORR) in alkaline media including: Co phthalocyanines (CoPc) [16], cobalt fullerene complexes [17], cobalt–iron–nitrogen chelate Co–C–N [18,19], cobalt-hexadecafluoro-phthalocyanine (CoPcF16) [20], polypyrrole-modified carbon-supported Co(OH) 2 -PPY-C/GC [21], Co containing precursor and a polypyrrole/C composite mate- rial (PPy/C) [22] and other cobalt macrocycles [23]. Most of the Co containing precursors and a polypyrrole/C com- posite material, exhibit a dual site functionality [22] where O 2 initially is reduced at a Co 2+ containing N–C type site in a 2e - pro- cess to form H 2 O 2 , which can react further in the series type ORR mechanism at the decorated Co x O y /Co nano-particle surface under- going either further electrochemical reduction to form OH - species or chemical disprotonation to form OH - species and molecular O 2 [22]. Rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) measurements have also showed that the ORR mechanism is via a 2e - pathway on most of the reported Co based catalyst in the literature with a Tafel slope of 120 mV dec -1 . Values for the number of electrons (n) in the ORR at the higher potential region (E < -100 mV vs. Hg/HgO) are reported to be ca. 2 for CoPc/C cat- alyst [20,24], in a range of 1.4–2.4 for CoPc/C [24,25], an apparent 2e - for CoPcF16 [20] and values between 2.4 and 3 for CoTAA [26]. Similarly, cobalt (II) porphyrins, TpOCH 3 PPCo, TpCF 3 PPCo and TpF- 0378-7753/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2011.04.045