title: Photoelectrochemical Water Splitting System--A Study of Interfacial Charge Transfer with Scanning Electrochemical Microscopy.
abstract: Fast charge transfer kinetics at the photoelectrode/electrolyte interface is critical for efficient photoelectrochemical (PEC) water splitting system. Thus, far, a measurement of kinetics constants for such processes is limited. In this study, scanning electrochemical microscopy (SECM) is employed to investigate the charge transfer kinetics at the photoelectrode/electrolyte interface in the feedback mode in order to simulate the oxygen evolution process in PEC system. The popular photocatalysts BiVO4 and Mo doped BiVO4 (labeled as Mo:BiVO4) are selected as photoanodes and the common redox couple [Fe(CN)6](3-)/[Fe(CN)6](4-) as molecular probe. SECM characterization can directly reveal the surface catalytic reaction kinetics constant of 9.30 × 10(7) mol(-1) cm(3) s(-1) for the BiVO4. Furthermore, we find that after excitation, the ratio of rate constant for photogenerated hole to electron via Mo:BiVO4 reacting with mediator at the electrode/electrolyte interface is about 30 times larger than that of BiVO4. This suggests that introduction of Mo(6+) ion into BiVO4 can possibly facilitate solar to oxygen evolution (hole involved process) and suppress the interfacial back reaction (electron involved process) at photoanode/electrolyte interface. Therefore, the SECM measurement allows us to make a comprehensive analysis of interfacial charge transfer kinetics in PEC system.
authors.affiliation: Wuhan National Laboratory for Optoelectronics, School of Optoelectronic Science and Engineering, Huazhong University of Science and Technology , Wuhan 430074, China.
authors.forename: Bingyan
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Wuhan National Laboratory for Optoelectronics, School of Optoelectronic Science and Engineering, Huazhong University of Science and Technology , Wuhan 430074, China.
authors.forename: Xiaofan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Wuhan National Laboratory for Optoelectronics, School of Optoelectronic Science and Engineering, Huazhong University of Science and Technology , Wuhan 430074, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Wuhan National Laboratory for Optoelectronics, School of Optoelectronic Science and Engineering, Huazhong University of Science and Technology , Wuhan 430074, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Shen
keywords: feedback mode; interfacial charge transfer; kinetics; photoelectrochemical water splitting; scanning electrochemical microscopy