Angewandte Chemie International Edition, 2014.
Justus Masa, Wei Xia, Ilya Sinev, Anqi Zhao, Zhenyu Sun, Stefanie Grützke, Philipp Weide, Martin Muhler, Wolfgang Schuhmann.
Analytische Chemie—Zentrum für Elektrochemie (CES), Ruhr-Universität Bochum, NC04/788, 44780 Bochum (Germany) &
Lehrstuhl für Technische Chemie, Ruhr-Universität Bochum, NBCF 04/690, 44801 Bochum (Germany).
Reversible interconversion of water into H2 and O2, and the recombination of H2 and O2 to H2O thereby harnessing the energy of the reaction provides a completely green cycle for sustainable energy conversion and storage. The realization of this goal is however hampered by the lack of efficient catalysts for water splitting and oxygen reduction. We report exceptionally active bifunctional catalysts for oxygen electrodes comprising Mn3O4 and Co3O4 nanoparticles embedded in nitrogen-doped carbon, obtained by selective pyrolysis and subsequent mild calcination of manganese and cobalt N4 macrocyclic complexes. Intimate interaction was observed between the metals and nitrogen suggesting residual M–Nx coordination in the catalysts. The catalysts afford remarkably lower reversible over potentials in KOH (0.1 m) than those for RuO2, IrO2, Pt, NiO, Mn3O4, and Co3O4, thus placing them among the best non-precious-metal catalysts for reversible oxygen electrodes reported to date.