The Interfacial Structure of InP(100) in Contact with HCl and H$_2$SO$_4$ studied by Reflection Anisotropy Spectroscopy

TL;DR

This study uses operando reflection anisotropy spectroscopy to investigate the interfacial structure of p-doped InP(100) surfaces in contact with HCl and H₂SO₄ electrolytes, revealing reversible oxide reduction and initial corrosion processes.

Contribution

It provides new insights into the electrochemical interface structure of InP(100) during potential cycling in different electrolytes using reflection anisotropy spectroscopy.

Findings

Reversible oxide reduction observed at low electrolyte concentrations.

Initial surface corrosion occurs at higher electrolyte concentrations.

Operando spectroscopy reveals dynamic interfacial structural changes.

Abstract

Indium phosphide and derived compound semiconductors are materials often involved in high-efficiency solar water splitting due to their versatile opto-electronic properties. Surface corrosion, however, typically deteriorates the performance of photoelectrochemical solar cells based on this material class. It has been reported that (photo)electrochemical surface functionalisation protects the surface by combining etching and controlled corrosion. Nevertheless, the overall involved process is not fully understood. Therefore, access to the electrochemical interface structure under operando conditions is crucial for a more detailed understanding. One approach for gaining structural insight is the use of operando reflection anisotropy spectroscopy. This technique allows the time-resolved investigation of the interfacial structure while applying potentials in the electrolyte. In this study, p-doped InP(100) surfaces are cycled between anodic and cathodic potentials in two different electrolytes, hydrochloric acid and sulphuric acid. For low, 10 mM electrolyte concentrations, we observe a reversible processes related to the reduction of a surface oxide phase in the cathodic potential range which is reformed near open-circuit potentials. Higher concentrations of 0.5 N, however, already lead to initial surface corrosion.