Front-Surface Potential of Platinized p‑InP Photocathodes Probed by Dual-Working-Electrode Measurements.

Area of Science:

• Photocatalysis
• Semiconductor interfaces
• Hydrogen evolution reaction

Background:

• p-InP/Pt photocathodes are promising for hydrogen evolution.
• Understanding their front-surface potential (Efr) is crucial for stability.
• Existing stability mechanisms require experimental validation.

Purpose of the Study:

• To probe the front-surface potential (Efr) of p-InP/Pt photocathodes under operating conditions.
• To validate proposed stability mechanisms for p-InP photocathodes.
• To establish a rapid, operando metric for interfacial catalyst activity.

Main Methods:

• Utilized a dual-working-electrode (DWE) method.
• Operated photocathodes under hydrogen evolution reaction conditions.
• Measured front-surface potential (Efr) and back-contact potential (Eb).

Main Results:

• DWE data align with proposed stability mechanisms for p-InP photocathodes.
• Efr for Pt-modified p-InP stabilizes near the reversible hydrogen electrode (RHE) potential.
• This potential suggests kinetic suppression of metallic In0 formation.
• Efr is governed by surface catalytic kinetics, not applied back-contact potential (Eb).

Conclusions:

• The DWE method provides a rapid, operando assessment of interfacial catalyst activity.
• Surface catalytic kinetics are the primary determinant of Efr in p-InP/Pt junctions.
• These findings support the proposed stability mechanisms for p-InP photocathodes.