The instability of the semiconductor-electrolyte interface is a major challenge for the development and implementation of long-lasting photoelectrochemical (PEC) solar fuel producing devices [1]. Kinetic studies, incorporating the competing photocorrosion and fuel producing reaction mechanisms at the photoelectrode of the PEC device, predicted that some thermodynamically unstable semiconductors could be kinetically stable as a result of their extremely low photocorrosion current and therefore enable acceptable lifetimes [2].

We developed a 1-D multi-physics model that coupled the reactions kinetics to photo-physical processes occurring in the PEC device. These processes include radiation absorption, charge carrier generation, charge transport, charge transfer from the semiconductor to the electrocatalyst, charge transport in the catalyst and photocorroded layers, and mass transport in the electrolyte phase. The model accounted for the impact of surface chemical properties, catalyst activity, charge carrier density in the semiconductor and in the electrocatalyst, and electrolyte acidity. In parallel, a bonding model was developed to predict the surface back-bond potential of the semiconductor, which is known in highly impact on the stability [2].

When applied to some promising semiconductors for photoelectrochemical water splitting, the model provided trends on the dependence of the stability of the semiconductor-electrolyte interface on irradiation intensity, semiconductor and electrocatalyst properties, and mass transport in the electrolyte.

[1] Fredy Nandjou and Sophia Haussener, Degradation in photoelectrochemical devices: review with an illustrative case study, Journal of Physics D: Applied Physics 50, 2017.

[2] Fredy Nandjou and Sophia Haussener, Kinetic Competition between Water‐Splitting and Photocorrosion Reactions in Photoelectrochemical Devices, ChemSusChem 12, 2019.