A Physics-Based Model to Investigate Degradation-Related Performance Loss in Photoelectrochemical Devices

Wednesday, 4 October 2017: 09:00
National Harbor 6 (Gaylord National Resort and Convention Center)
F. Nandjou (Lab. of Renewable Energy Science & Engg. (LRESE), EPFL) and S. Haussener (EPFL)
Understanding and mitigating performance loss in photoelectrochemical devices are key factors for advancing their large-scale implementation and industrialization. Performance loss is caused not only by the degradation of single components (semiconductor, catalyst and electrolyte), but also by the interplay between the operating conditions and the various degradation phenomena. While the catalyst and electrolyte degradations are considerable challenges for long-term durability, the short-term durability mainly depends on the semiconductor material and its interface with the electrolyte [1]. Semiconductors with good photoabsorption behavior and interesting band alignments are inherently non-stable, and therefore degrade within hours due to photocorrosion.

Usually, photocorrosion is interpreted on the basis of energy schemes, comparing the quasi-Fermi levels of minority carriers to the corrosion potentials of the photoelectrode [2]. However, the competition between the pure redox process of water splitting and photoelectrode dissolution/passivation is mainly determined by kinetic parameters [3].

In this study, we use a physics-based model to quantify the effect of photocorrosion phenomenon on the global performance loss of the photoelectrochemical device. The studied device is composed of different catalyst covered semiconductors, immersed in a liquid electrolyte. The catalyst layer is considered a nanoporous media, the solid phase being composed of a supporting structure and catalyst particles.

The simulation results highlight the practical limitation of using thermodynamic calculations for the investigation of photoelectrochemical devices durability, and how irradiation, mass transport, and kinetic properties can impact the stability of the photoelectrode/electrolyte interface.

[1] F. Nandjou and S. Haussener. Degradation in photoelectrochemical devices: Review with an illustrative case study. J. Phys. D: Appl. Phys. 50 (2017) 124002.

[2] H. Gerischer et al. Report EUR 9531 EN (1984), Commission of the European Communities.

[2] R. Memming. The Role of Energy Levels in SemiconductorElectrolyte Solar Cells. J. Electrochem. Soc. 125 (1978) 117.