Operational Spectroelectrochemical Investigation on the Interfacial Charge Dynamics of Copper Bismuth Oxide Based Photocathode

Abstract

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.

Photoelectrochemical properties of p-type CuBi2O4 prepared by spray pyrolysis of carbon-free precursor aqueous solution combined with post-annealing treatment

“…Surface modifications, such as the addition of a protective layer and a cocatalyst, serve as advanced strategies to prevent surface photocorrosion and promote the electron transfer process (such as the HER and CO 2 -reduction); these also mitigate photocorrosion during the PEC operation. 43,51,52,64 To further clarify the structure–activity and carrier transfer processes of CBO under light excitation, spectroscopic techniques such as photoluminescence (PL) emission spectroscopy, 40 pump–probe spectroscopy, 42 and AC impedance spectroscopy 65 should be employed. These comprehensive investigations will be performed in a future study aiming to provide an in-depth insight into the physicochemical properties of CBO and enhance its PEC energy conversion efficiency.…”

Enhanced hydrogen evolution reaction via photoelectrochemical water splitting utilizing asymmetric MoSSe under a low external magnetic field

“…To corroborate our proposition of low recombination in the MoSSe/SiNW PC under an external magnetic eld, we have followed the photo response study through chronoamperometry under chopped illumina-Effective carrier lifetime and surface recombination can be understood from the photocurrent response under chopped illumination. 62,63 Here we have compared the pristine SiNW PC, MoSSe/SiNW PC and MoSSe/SiNW PC under a 0.4 T external magnetic eld. In the applied bias region where photocurrent is signicant, the photocurrent response to chopped illumination does not possess ideal rectangular behavior, rather possesses decay and overshoot behavior with light on and off.…”

“…The sharp spike can be attributed to the accumulation of minority carriers (electrons) at or near the surface/interface and the decay can be attributed to huge surface recombination loss. 62,63 A steady state is reached when the accumulation rate is exactly countered by recombination loss and charge transfer to the electrolyte. 62 In the case of MoSSe/SiNW, we observed similar decay behavior with comparatively less surface recombination (Fig.…”