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

## TL;DR

This study uses a new method to measure the surface potential of a material used for hydrogen production, showing how catalyst activity affects its performance.

## Contribution

The paper introduces a dual-working-electrode method to measure the front-surface potential of platinized p-InP photocathodes under operating conditions.

## Key findings

- The front-surface potential of Pt-modified p-InP is near the reversible hydrogen electrode potential.
- The surface potential is governed by catalytic kinetics, not the back-contact potential.
- The method provides a rapid, operando metric for interfacial catalyst activity.

## Abstract

The front-surface potential (E
fr) of p-InP/Pt photocathodes
performing the hydrogen-evolution
reaction has been probed under operating conditions using a dual-working-electrode
(DWE) method. The DWE data are consistent with expectations for proposed
stability mechanisms for p-InP photocathodes. Specifically, E
fr for Pt-modified p-InP adopts
a value near the reversible hydrogen electrode (RHE) potential, consistent
with kinetic suppression of metallic In0 formation. The
data provide a rapid, operando metric of interfacial catalyst activity,
and indicate that E
fr for the p-InP/Pt junction is governed by surface catalytic kinetics
rather than by the applied back-contact potential (E
b).