ABSTRACT
Cobalt hydroxides, Co(OH)2, have attracted considerable attention due to their diverse applications in the fields of energy and the environment. However, probing the electronic structure of Co(OH)2 is challenging, mainly due to its sensitivity to electron beam irradiation. In this study, we report the unperturbed O K-edge and Co L-edge for Co(OH)2 by electron beam damage and investigate the electronic structure transformation of Co(OH)2 under electron beam irradiation, using low current electron energy loss spectroscopy. In particular, the O K-edge pre-peak at 530 eV, which is not found in the undamaged Co(OH)2, begins to appear with an increasing electron beam current. In addition, the Co L-edge peak shifts to a higher energy, close to Co3O4, indicating that the localized phase transition within Co(OH)2 leads to the formation of Co3O4.
ABSTRACT
A BiVO4/Bi2S3 composite comprising Bi2S3 nanowires on top of a BiVO4 film was prepared via hydrothermal reaction. Because additional Bi3+ ions were not delivered during the reaction, BiVO4 served as the Bi3+ ion source for the development of Bi2S3. A detailed growth mechanism of the nanowire was elucidated by an analysis of the concentration gradient of Bi3+ and S2- ions during the reaction. The in situ growth was followed by the etching of BiVO4 to Bi3+ and VO43- ions and regrowth to Bi2S3, which resulted in the rapid evolution of nanowires on the BiVO4 substrate. The fabricated BiVO4/Bi2S3NW composite exhibited an improved photoelectrochemical activity compared to other Bi2S3 samples. The improved efficiency was mainly attributed to both improved charge separation and effective adhesion obtained by the in situ growth.
ABSTRACT
A pinhole-free BiVO4 electrode was successfully synthesized using an ultrasonic-assisted synthetic method on a conductive substrate. The pinhole-free BiVO4 electrode showed highly improved photoelectrochemical activity for both sulfite oxidation and water oxidation. The blocking recombination processes were examined to clarify the enhanced photoelectrochemical performances.
ABSTRACT
The addition of water initiates the phase transition of hexagonal CoO to Co(OH)2 nanocrystals. Inducing the phase transition of h-CoO on various substrates results in efficient chemical bonding between Co(OH)2 and the substrate. The efficient deposition of Co(OH)2 is widely applicable for electrochemical and photoelectrochemical water oxidation reactions.
