Failure Modes of Platinized pn+‑GaInP Photocathodes for Solar-Driven H2 Evolution

• Published in: ACS applied materials & interfaces Vol. 14; no. 23; pp. 26622 - 26630
• Main Authors: Yu, Weilai, Buabthong, Pakpoom, Young, James L., Ifkovits, Zachary P., Byrne, Sean T., Steiner, Myles A., Deutsch, Todd G., Lewis, Nathan S.
• Format: Journal Article
• Language: English
• Published: American Chemical Society 15.06.2022
• Subjects: Energy, Environmental, and Catalysis Applications; III−V semiconductor; photoelectrochemistry; water splitting; failure mode; solar fuels
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.2c01845

The long-term stability for the hydrogen-evolution reaction (HER) of homojunction pn+-Ga0.52In0.48P photocathodes (band gap = 1.8 eV) with an electrodeposited Pt catalyst (pn+-GaInP/Pt) has been systematically evaluated in both acidic and alkaline electrolytes. Electrode dissolution during chronoamperometry was correlated with changes over time in the current density-potential (J–E) behavior to reveal the underlying failure mechanism. Pristine pn+-GaInP/Pt photocathodes yielded an open-circuit photopotential (E oc) as positive as >1.0 V vs the potential of the reversible hydrogen electrode (RHE) and a light-limited current density (J ph) of >12 mA cm–2 (1-sun illumination). However, E oc and J ph gradually degraded at either pH 0 or pH 14. The performance degradation was attributed to three different failure modes: (1) gradual thinning of the n+-emitter layer due to GaInP dissolution in acid; (2) active corrosion of the underlying GaAs substrate at positive potentials causing delamination of the upper GaInP epilayers; and (3) direct GaAs/electrolyte contact compromising the operational stability of the device. This work reveals the importance of both substrate stability and structural integrity of integrated photoelectrodes toward stable solar fuel generation.