(544gz) Probing the (Photo)Electrochemical Stability of Atomic Layer Deposited Coatings for Solar-Driven Hydrogen Evolution
AIChE Annual Meeting
2018
2018 AIChE Annual Meeting
Catalysis and Reaction Engineering Division
Poster Session: Catalysis and Reaction Engineering (CRE) Division
Wednesday, October 31, 2018 - 3:30pm to 5:00pm
In this work, we investigate the (photo)electrochemical stability of several canonical metal oxide and chalcogenide protective coatings deposited by ALD, including titania (TiO2) and molybdenum disulfide (MoS2). Experiments are conducted in both standalone electrochemical testing and photoelectrochemical testing when combined with thin film chalcopyrite (CuGaxSey) photocathodes. Through x-ray photoelectron spectroscopic (XPS) interrogation of as-prepared samples and of those that have undergone electrochemical testing, some surprising results emerge. While ALD-deposited TiO2 has imparted good stability to photoanodes under oxygen-evolving potentials in basic conditions,1,2 our ultra-thin film (5 nm) amorphous TiO2 coatings completely degrade on the order of hours at hydrogen-evolving potentials in acidic conditions, and over a couple of days at hydrogen-evolving potentials in near-neutral conditions. Similarly, amorphous molybdenum trioxide (MoO3)-derived MoS2 coatings were shown to be dramatically less stable than Mo metal-derived MoS2 coatings under hydrogen-evolving potentials in acidic conditions. High temperature anneals were shown to have a marked stabilizing influence on the hydrogen-evolving performance of the ALD-deposited coatings; for TiO2, the initial degradation rate was slowed by at least a factor of five. Finally, promising next-generation oxide and chalcogenide coatings for hydrogen evolution were also examined and their results are presented herein.
1 Chen, Y. W., Prange, J. D., Dühnen, S., Park, Y., Gunji, M., Chidsey, C. E. D., & McIntyre, P. C. (2011). Atomic layer-deposited tunnel oxide stabilizes silicon photoanodes for water oxidation. Nature Materials, 10(7), 539â544.
2 Hu, S., Shaner, M. R., Beardslee, J. A., Lichterman, M., Brunschwig, B. S., Lewis, N. S., ⦠Wallrapp, F. (2014). Amorphous TiO2 coatings stabilize Si, GaAs, and GaP photoanodes for efficient water oxidation. Science (New York, N.Y.), 344(6187), 1005â9.