support IL layer metal particle/center Improved electrochemical perfor- mance of Fe-N-C catalysts through ionic liquid modification in alkaline media Thomas Wolker, Ioanna Martinaiou, Ali Shahraei, Gui-Rong Zhang, A. Janßen, Stephan Wagner, Natascha Weidler, Robert W. Stark, Bastian J.M. Etzold*, Ulrike I. Kramm Electrochemistry 2018, 24.-26.09.2018, Ulm correspondence: Prof. Dr.-Ing. B.J.M. Etzold email: etzold@tu-darmstadt.de Ernst-Berl-Institut phone: +49 (0) 6151 / 16-29984 Alarich-Weiss-Str. 8 fax: +49 (0) 6151 / 16-29982 D-64287 Darmstadt http: www.etzoldlab.de literature: [1] Y. Nie, L. Li, Z. Wei, Chem. Soc. Rev. 44 (2015) [2] G.R. Zhang, M. Munoz, B.J.M. Etzold, ACS Appl. Mater. Interfaces 7 (2015) [3] G.R. Zhang, M. Munoz, B.J.M. Etzold, Angew. Chem. Int. Ed. 55 (2016) [4] I. Martinaiou, T. Wolker, B.J.M. Etzold, et al., J. Power Sources 375 (2018) Highly active oxygen reduction reaction (ORR) electrocatalysts that are stable under operating conditions are needed in order to enable a widespread commercialization of the fuel cell technology. State-of-the-art ORR catalysts are mostly based on platinum. Due to their high price noble-metal-free alternatives are highly desirable [1]. Carbon-based materials emerge as one of the promising candidates due to their remarkable advantages of low cost, abundant structural variety, tailorable surface chemistry, and good conductivity. Transition metal-nitrogen-carbon catalysts (e.g. Fe-N-C) are considered as one of the most promising representatives of this catalyst class. However, these systems often show a poor stability during electrochemical cycling and therefore still need to be improved in order to replace state-of-the- art noble metal catalysts. Quite recently we have demonstrated that filling the pores of Pt/C catalysts by a minor amount of Ionic Liquid ([BMIM][NTf2], [MTBD][NTf2]) would significantly boost the catalytic activity of Pt/C for ORR [2,3]. This was explained by the fact that the modification led to a new microenvironment around active centers that would prevent the poisoning with oxygenated species. Inspired by this work, herein we transfer this strategy to the Fe-N-C catalysts [4]. § Fe-N-C catalysts with and without sulfur were prepared § Sulfur addition led to a slightly increased micropore volume § Modification of sulfur free catalysts with [BMMIM][NTf2] increased the catalytic ORR- activity in a similar range as sulfur addition § The different behavior of the sulfur containing catalyst could be explained by pore blocking effects § IL modification could thus be an interesting way to obtain highly active and stable noble- metal free electrocatalysts for fuel cell aplications Introduction Oxygen Reduction Reaction Solid Catalysts with Ionic Liquid Layer (SCILL concept) α = 0 α = 10% α: pore filling degree α = VIL/Vpore,0 The pores of a catalyst are partially filled with Ionic Liquid to create a new microenvironment around active centers Highly active catalyst needed to overcome sluggish kinetics Selectivity towards 4 e- - pathway desired Conclusions O2 OH- HO2- O2 OH- HO2- 2e- 2e- 4e- O2 H2O H2O2 2e- 2e- 4e- Alkaline Acidic Dicyandiamide Iron acetate Phenanthroline Thermal decomposition 800 °C Acid leaching 2nd heat treatment Fe-(S)-N-C Sulfur ( ) ( ) Catalyst Synthesis and Modification Fe-(S)-N-C-SCILL Unreactive species Textural Characterization SBET /m2 g-1 SMicropore /m2 g-1 SMesopore /m2 g-1 VPore /cm3 g-1 -S 416 218 201 0.49 +S 442 299 165 0.44 Nitrogen sorption revealed similar textural properties Electrocatalytic Performance IL Modification can cause similar boosting as sulfur Stability can also be improved by IL addition [BMMIM][NTf2] TW, GRZ and BE acknowledge funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement n° 681719) Acknowledgment + IL