CuBi2O4 for solar water reduction: an IMPS analysis
Ingrid Rodríguez-Gutiérrez a, Manuel Rodríguez-Pérez a, Rodrigo García-Rodríguez a, Alberto Vega-Poot a, Geonel Rodríguez-Gattorno a, Bruce A. Parkinson b, Gerko Oskam a
a Department of Applied Physics, CINVESTAV-IPN, Ant. Carr. a Progreso km 6, Cordemex, Mérida, Yucatán, 97310, Mexico
b Department of Chemistry, University of Wyoming, Laramie, WY, USA, Laramie, Wyoming 82071, EE. UU., Laramie, United States
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV18)
Benidorm, Spain, 2018 May 28th - 31st
Organizers: Emilio Palomares and Rene Janssen
Oral, Gerko Oskam, presentation 044
DOI: https://doi.org/10.29363/nanoge.hopv.2018.044
Publication date: 21st February 2018

Solar-driven hydrogen production via water splitting is a promising technology for a future solar fuel economy. The development of efficient, stable, economical and abundant p-type semiconductor materials is essential, and one of the principal challenges is to improve the solar-to-hydrogen conversion efficiency, which is generally limited by either a low light harvesting efficiency (high band gap) or an unfavorable kinetic balance of slow charge transfer to the solution and fast recombination. In this work, combinatorial chemistry has been employed to select a Cu-Bi ternary oxide that could be a suitable option for a solar water splitting system. CuBi2O4 photoelectrodes have been deposited by inkjet printing and the photoelectrochemical properties have been studied in detail using intensity-modulated photocurrent spectroscopy (IMPS). In the current –potential curves, a steady-state photocurrent corresponding to water reduction at p-type CuBi2O4 is observed, with an onset at 0.75 V vs RHE; the maximum current density obtained for a 280 nm film at 0.2 V vs. RHE was 0.12 mA cm-2. In the hydrogen photogeneration potential range, IMPS illustrates that the recombination rate constant is larger than that corresponding to electron transfer to the solution, resulting in a relative transfer efficiency between 0.2 - 0.4, explaining the relatively low photocurrent. The results illustrate the promise of this p-type oxide for application in a tandem solar water splitting device, and strategies to improve the efficiency are discussed. IMPS analysis illustrate that at sufficiently positive applied potential (> 0.8 V vs RHE), the CuBi2O4 response is characteristic of an n-type semiconductor showing a photo-oxidation process, however, the rate constant for hole transfer to the solution is small resulting in a negligible steady state anodic photocurrent.

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