Photodegradation of CuBi₂ O₄ Films Evidenced by Fast Formation of Metallic Bi using Operando Surface-sensitive X-ray...

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• Copper bismuth oxide (CuBi2O4) is a promising photocathode material for photo-electrochemical (PEC) water splitting.
• Rapid degradation of CuBi2O4 under operational conditions limits its practical application.

Purpose of the Study:

• To investigate the degradation mechanisms of CuBi2O4 photocathodes during PEC water splitting.
• To establish a method for studying the semiconductor-electrolyte interface operando.

Main Methods:

• Utilized surface-sensitive high-energy X-ray scattering to study the CuBi2O4 semiconductor-electrolyte interface during PEC operation.
• Correlated photocurrent changes with structural and chemical transformations of the electrode.

Main Results:

• Identified the formation of metallic bismuth (Bi) as the primary cause of rapid photocurrent decrease.
• Observed slower formation of metallic copper (Cu) and electrode dissolution contributing to activity and morphology changes.
• Provided a detailed understanding of CuBi2O4 photocathode degradation pathways.

Conclusions:

• The study elucidates the critical role of metallic Bi phase formation in CuBi2O4 photocathode failure.
• The developed operando X-ray scattering technique offers a basis for investigating photocorrosion in diverse PEC materials.
• Addressing these degradation mechanisms is essential for advancing CuBi2O4 and other PEC materials for water splitting.