Luo, F.; Roy, A.; Silvioli, L.; Cullen, D.A.; Zitolo, A.; Sougrati, M.T.; Oguz, I.C.; Mineva, T.; Teschner, D.; Wagner, S.; Wen, J.; Dionigi, F.; Kramm, U.I.; Rossmeisl, J.; Jaouen, F.; Strasser, P.: P-block single-metal-site tin/nitrogen-doped carbon fuel cell cathode catalyst for oxygen reduction reaction. Nature Materials 19 (2020), p. 1215-1223
10.1038/s41563-020-0717-5
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Abstract:
This contribution reports the discovery and analysis of a p-block Sn-based catalyst for the electroreduction of molecular oxygen in acidic conditions at fuel cell cathodes; the catalyst is free of platinum-group metals and contains single-metal-atom actives sites coordinated by nitrogen. The prepared SnNC catalysts meet and exceed state-of-the-art FeNC catalysts in terms of intrinsic catalytic turn-over frequency and hydrogen–air fuel cell power density. The SnNC-NH3 catalysts displayed a 40–50% higher current density than FeNC-NH3 at cell voltages below 0.7 V. Additional benefits include a highly favourable selectivity for the four-electron reduction pathway and a Fenton-inactive character of Sn. A range of analytical techniques combined with density functional theory calculations indicate that stannic Sn(iv)Nx single-metal sites with moderate oxygen chemisorption properties and low pyridinic N coordination numbers act as catalytically active moieties. The superior proton-exchange membrane fuel cell performance of SnNC cathode catalysts under realistic, hydrogen–air fuel cell conditions, particularly after NH3 activation treatment, makes them a promising alternative to today’s state-of-the-art Fe-based catalysts.