Synergistic Effects of Surface Passivation and Charge Separation to Improve Photo-electrochemical Performance of BiOI Nanoflakes by Au Nanoparticle Decoration
An-Mi Chang, Yu‐Hung Chen, Chien‐Chih Lai, Ying‐Chih Pu
Abstract
We demonstrate that the photoactivity of bismuth oxyiodide (BiOI) nanoflake (NF) photocathodes in photo-electrochemical (PEC) water splitting can be significantly enhanced by about 24-fold by thermal calcination under an air atmosphere and then surficial decoration of Au nanoparticles (NPs). To understand the key factors affecting the PEC efficiency in Au NP-decorated BiOI NF photoelectrodes, incident photon-to-current conversion efficiency, electrochemical impedance spectroscopy, photovoltage, and electrochemically active surface area measurements were performed. The analytic results presented that thermal calcining could produce mesopores, increasing active sites on the surface of BiOI NFs. In addition, the synergistic effects of surface-state passivation and charge separation were observed for the surficial Au NP decoration on BiOI NFs. Transient absorption spectroscopy coupled with PEC measurements confirmed that the lifetime of photogenerated electrons on the conduction band of BiOI NFs can be prolonged by Au NP decoration, resulting in higher probability to carry out water reduction. The current investigation presents important insights into the mechanism of charge carrier dynamics in metal-semiconductor nano-heterostructures, which is contributive to develop photoelectrode materials in solar fuel production.