FIGURE 2 PHYSICOCHEMISTRY OF LIQUIDS, SOFT MATTER, NANOCHEMISTRY SYNCHROTRON SOLEIL HIGHLIGHTS 2020 SAMBA BEAMLINE Associated publication P-block single- eta-site tin/nitrogen- doped carbon fuel cell cathode catalyst for oxygen reduction reaction. Sn(IV) species. It must be pointed out that 119Sn Mössbauer spectroscopy F. Luo, A. Roy, L. Silvioli, D. A. Cullen, was for the first time employed to study the novel Sn-N-C catalysts, A., Zitolo, M. T. Sougrati, I. Can Oguz, in contrast to 57Fe Mössbauer spectroscopy, already widely applied to T. Mineva, D. Teschner, S. Wagner, study Fe-N-C catalysts.[5] J. Wen, F. Dionigi, U. I. Kramm, J. Rossmeisl, F. Jaouen & P. Strasser. First principle DFT calculations allowed us ruling out tin oxide and Nature Materials, 19, 1215 (2020). metallic Sn as active species in Sn-N-C, but rather suggested pyridinic N-coordinated central Sn atoms embedded in a carbon matrix as the References most likely catalytic centres (Figure 3). Moreover, DFT calculations of119Sn [1] W. Sung et Mössbauer spectroscopy response for various SnN sites assigned the al. , SAE Int. J. Engines Sn(IV) species mainly to gas-phase accessible SnN moieties stronglyx 3.1, 768 (2010). x [2] M. Lefevre et al., Science 324, binding O.2 71 (2009). [3] G. Wu et al., Science 332, The discovery of highly active Sn-based materials for the ORR extends 443 (2011). the horizon of possible non-PGM fuel cell cathode catalysts as suitable [4] C. W. B. Bezerra et al., Electrochim. Pt substitutes, and facilitates innovative synthetic routes design. Acta 53, 4937 (2008). [5] J. Li et al., Nature Catalysis 4, 10 (2021). FIGURE 3 Corresponding authors Peter Strasser Department of Chemistry, The Electrochemical Energy, Catalysis and Material Science Laboratory, Chemical Engineering Division,Technical University, Berlin, Germany. pstrasser@tu-berlin.de Frédéric Jaouen ICGM, Univ. Montpellier, CNRS, ENSCM Montpellier, France. frederic.jaouen@umontpellier.fr Captions FIGURE 1: PEMFC polarization curves for Sn-N-C, Fe- N-C, and Co-N-C after NH3 activation. FIGURE 2: a) Sn K-edge EXAFS analysis in the Fourier Transformed space of Sn-N-C. The black curve represents the experimental spectrum while the red curve represents the calculated spectrum based on the depicted structure. b) Comparison between the Sn K-edge XANES experimental spectrum of Sn-N-C (red line), SnO (blue line), and SnO2 (dark green line). Black triangles identify the experimental edge positions. FIGURE 3: DFT-optimized cluster model of a Sn-N4 site in the Sn-N-C catalyst. 39