- Research
BiMn2O5: A stable solar fuels photoanode with ideal band gap
Newhouse, P. F., Reyes-Lillo, S. E., Li, G., Zhou, L., Shinde, A., Guevarra, D., Suram, S. K., Soedarmadji, E., Richetr, M. H., Qu, X., Persson, K., Neaton, J. B., Gregoire, J. M. Discovery and Characterization of a Pourbaix Stable, 1.8 eV Direct Gap Bismuth Manganate Photoanode. Chem. Mater, DOI: 10.1021/acs.chemmater.7b03591 (2017).
Scientific Achievement
Combining high throughput experimentation with theory enabled discovery of a unique solar fuels photoanode with strong visible light absorption and remarkable stability.
Significance & impact
Semiconductors with a band gap in the visible range are typically unstable at water oxidation potentials, making this 1.8 eV direct-gap photoanode an unprecedented discovery.
Research Details
The discovery was made in an inkjet-printed combinatorial library where BiMn2O5 was revealed as the active photoanode whose alloy with Sm improves photoactivity.
The Pourbaix-stable region extends 13 pH units at 1.23 vs RHE
The electronic structure resembles that of BiVO4 with similar valence band hybridization and V d states replaced by Mn d.
Reprinted with permission from Newhouse, P. F., Reyes-Lillo, S. E., Li, G., Zhou, L., Shinde, A., Guevarra, D., Suram, S. K., Soedarmadji, E., Richetr, M. H., Qu, X., Persson, K., Neaton, J. B., Gregoire, J. M. Discovery and Characterization of a Pourbaix Stable, 1.8 eV Direct Gap Bismuth Manganate Photoanode. Chem. Mater, DOI: 10.1021/acs.chemmater.7b03591 (2017).
Solar-driven oxygen evolution is a critical technology for renewably synthesizing carbon fuels. New photoanode materials are needed to meet efficiency and stability requirements, motivating materials explorations for semiconductors with (i) band-gap energy in the visible spectrum and (ii) stable operation in aqueous electrolyte at the electrochemical potential needed to evolve oxygen from water. We explore the Bi–Mn–Sm oxide system for new photoanodes. Through the use of a ferri/ferrocyanide redox couple in high-throughput screening, BiMn2O5 and its alloy with Sm are identified as photoanode materials with a near-ideal optical band gap of 1.8 eV. Using density functional theory-based calculations of the mullite Bi3+Mn3+Mn4+O5 phase, we identify electronic analogues to the well-known BiVO4 photoanode and demonstrate excellent Pourbaix stability above the oxygen evolution Nernstian potential from pH 4.5 to 15. Our suite of experimental and computational characterization indicates that BiMn2O5 is a complex oxide with the necessary optical and chemical properties to be an efficient, stable solar fuel photoanode. T