Finding efficient non-expensive materials for the electrocatalytic oxygen evolution reaction in alkaline media is one of the major challenges in the development of green energy conversion technologies. Transition metal oxides represent an attractive alternative to the state of the art noble metal-based catalysts due to their high abundance, low cost, and wide versatility regarding structure, composition, oxidation state, morphology and surface area. However, a major drawback of most transition metal oxides is their poor electric conductivity, which hinders their electrocatalytic properties.

In this context, we present manganese oxide-based materials as alternative oxygen evolution electrocatalysts and we discuss different synthesis routes which aim, firstly, to overcome their conductivity limitations, and, secondly, to improve their overall performances regarding activity and stability, by embedding metal oxide particles in a conductive carbon matrix, such as few-layer graphene^[1] or carbon nanotubes^[2], followed by a thermal treatment step^[3]. Since it has been reported that the presence of metal impurities in the carbon supports can substantially promote the electrocatalytic activity of carbon containing catalysts^[4,5], we include as a design strategy the incorporation of small amounts of metal particles, such as iron, cobalt and nickel, into the manganese oxide-based composites, and we further discuss their impact on the overall electrocatalytic performance. Finally, we demonstrate the importance of coupling electrochemical methods with spectroscopic techniques for an in-depth characterization of the electrocatalytic materials under reaction conditions.

References:

[1] D.M. Morales, J. Masa, C. Andronescu, Y.U. Kayran, Z. Sun, W. Schuhmann, Electrochim. Acta 222 (2016) 1191–1199.

[2] K. Elumeeva, M. Kazakova, D.M. Morales, D. Medina, A. Selyutin, G. Golubtsov, Y. Ivanov, V. Kuznetzov, A. Chuvilin, H. Antoni, M. Muhler, W. Schuhmann J. Masa, ChemSusChem (2018) DOI: 10.1002/cssc.201702381.

[3] J. Masa, W. Xia, I. Sinev, A. Zhao, Z. Sun, S. Grützke, P. Weide, M. Muhler, W. Schuhmann, Angew. Chem. Int. Ed. 53 (2014) 8508–8512.

[4] M. Pumera, H. Iwai, J. Phys. Chem. C 113 (2009) 4401–4405.

[5] C.H.A. Wong, Z. Sofer, M. Kubesova, J. Kucera, S. Matejkova, M. Pumera, Proc. Natl. Acad. Sci. U.S.A. 111 (2014) 13774–13779.

Acknowledgment: The authors are grateful to the BMBF in the framework of the project “Mangan” (FKZ 03EK3548). D. M. Morales acknowledges the financial support from Deutscher Akademischer Austauschdienst (DAAD) and from Consejo Nacional de Ciencia y Tecnología (CONACyT).