Copper
bismuth oxide (CBO) is an emerging photocathode in photoelectrochemical
(PEC) water splitting but exhibits limited performance due to the
severe recombination of photogenerated charges at the semiconductor–liquid
junction (SCLJ). For the first time, a set of operational spectroelectrochemical
experiments including electrochemical impedance spectroscopy (EIS),
transient photocurrent spectroscopy (TPS), and intensity-modulated
photocurrent/voltage spectroscopy (IMVS, IMPS) are designed to investigate
the charge dynamics at the SCLJ. It is indicated that there are dense
surface states above the valence band of CBO, inducing the “Fermi
level pinning” (FLP) effect at the SCLJ. The kinetic parameters
speculated by IMVS and IMPS indicate the charge transfer efficiency
of below 10% with even a bias of ∼0.7 V applied. TPS confirms
the sluggish dynamics because of the charging behavior of the surface
states. It is expected that this work would provide new connotations
of charge dynamics at the SCLJ for the further optimization of CBO-based
PEC systems.
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