MnOx-based material development for photocatalytic application

Niklas Cibura, Max Planck Institute for Chemical Energy Conversion, Mülheim a. d. Ruhr, Germany
Simon Ristig, Max Planck Institute for Chemical Energy Conversion, Mülheim a. d. Ruhr, Germany
Jennifer Strunk, Max Planck Institute for Chemical Energy Conversion, Mülheim a. d. Ruhr, Germany

Manganese oxides are promising candidates for materials science since there is a wide range of reported physico-chemical properties, different possible oxidation states, crystal structures and polymorphs.[1] The application of manganese oxide based materials in photocatalysis faces the challenge of a wide spectrum of reported results, for instance various particle sizes, surface characteristics and diverging band gap energies (e.g. 1.2 - 3.7 eV for Mn2O3 materials).[2-5] On the other hand, the diversity of parameters implicates the accessibility of MnOx-species with an electronic structure suitable for sunlight-driven catalytic reactions and other presumably crucial characteristics, such as a large number of adsorption sites. To achieve such a desired system, it is imperative to define the synthesis parameters carefully to understand the impact of the material properties on the photocatalytic performance.

For this purpose, a systematic and reproducible approach is in progress to generate nanoscopic manganese oxide species in size regimes of tens of nanometers down to molecular single sites that are stabilized on a mesoporous SiO2-support. Apart from a thorough bulk characterization, the performance-related properties of the MnOx-based systems are estimated by characterizing the adsorption properties with probe molecules. As there are different requirements for the successful application in established photocatalytic fields, like organic waste degradation and energy conversion by means of water splitting, the materials performance is tested in a multitude of model reactions such as dye degradation, CO2 reduction and oxygen evolution reaction.

[1] S. Ristig, N. Cibura, J. Strunk; Green 2015, 5, 23.
[2] N. M. Hosny, A. Dahshan, Materials Chemistry and Physics 2012, 137, 637.
[3] Q.-u.-a. Javed, W. Feng-Ping, M. Y. Rafique, A. M. Toufiq, M. Z. Iqbal, Chinese Physics B 2012, 21, 117311.
[4] Q. Javed, F. P. Wang, M. Y. Rafique, A. M. Toufiq, Q. S. Li, H. Mahmood, W. Khan, Nanotechnology 2012, 23, 415603.
[5] H. Zhang, Z. Ji, T. Xia, H. Meng, C. Low-Kam, R. Liu, S. Pokhrel, S. Lin, X. Wang, Y.-P. Liao et al., ACS Nano 2012, 6, 4349.

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