Cation Vacancy-Mediated Ultrafast Hole Transport in CuBi₂O₄ Photocathodes

Area of Science:

• Materials Science
• Photocatalysis
• Solid-State Chemistry

Background:

• Tetragonal CuBi2O4 (CBO) is a promising photocathode material.
• Its intrinsic p-type conductivity, arising from cation vacancies, can limit hole utilization.

Purpose of the Study:

• To investigate the ultrafast transport dynamics of valence band holes in CBO photocathodes.
• To understand how atomic composition and p-type character manipulation affect hole transport and photocurrent.

Main Methods:

• Comprehensive ultrafast optical transient absorption spectroscopy (TAS) was employed.
• Both ex situ and in situ TAS experiments were combined with photoelectrochemical (PEC) performance tests.
• Compositional manipulation of CBO was performed.

Main Results:

• The study revealed polaron formation tendencies of valence band holes at cationic vacancy sites.
• Ultrafast hole transport dynamics were elucidated.
• Insights into the hindrance of photocurrent generation in CBO were provided.

Conclusions:

• Cation vacancies in CBO are critical sites for polaron formation, hindering efficient hole utilization.
• Understanding these dynamics is crucial for optimizing CBO photocathodes for enhanced performance.