Abstract
Two-dimensional layered K4Nb6O17 (KN) was easily formed as a secondary phase caused by the volatilization of alkali metal ions, when preparing ferroelectric KxNa1−xNbO3 based ceramics and films. In this work, it was believed that KN film is with weak ferroelectricity and has a little effect on the ferroelectric properties of KxNa1−xNbO3 based films. Moreover, temperature dependent (77–500 K) dielectric functions of KN film have been firstly extracted by fitting ellipsometric spectra with the Adachi dielectric function model and a four-phase layered model. The high-frequency dielectric constant linearly increases and optical band gap slightly decreases with increasing the temperature. We also research its photoelectrochemical properties and its application in high-efficient light-induced H2 evolution. In addition, X-ray photoelectron spectroscopy, Raman scattering, temperature dependent transmittance and infrared reflectance spectra, and first-principles calculation were conjointly performed to further reveal the intrinsic optoelectronic features and relevant mechanisms of KN.
Highlights
Since the discovery of graphene, two-dimensional (2D) layered materials such as metal chalcogenides, black phosphorus, transition metal oxides, and other 2D materials have raised great research interest due to their unique optical and electrical properties[1,2,3,4,5]
KN can be synthesized by various methods, especially the conventional solid-state reaction method, which was frequently adopted to prepared KN for the studies of photocatalytic hydrogen production[19, 31, 32]
After carefully checking the diffraction peaks of KN nanolaminas (KN-NL) and KN-Pt with different standard powder X-ray diffraction (XRD) patterns, it was believed that the XRD patterns of KN-NL and KN-Pt were more like K4Nb6O17 (JCPDS No 76-0977) and K4Nb6O17-3H20 (JCPDS No 21-1297), respectively
Summary
Since the discovery of graphene, two-dimensional (2D) layered materials such as metal chalcogenides, black phosphorus, transition metal oxides, and other 2D materials have raised great research interest due to their unique optical and electrical properties[1,2,3,4,5]. Considering that there are a few reports on modified hydrothermal method focusing on the photocatalytic H2 production for KN, so it raise that the hydrogen production rate are urgently desired to improve[9] These relevant kinetics mechanisms should be detailedly investigated to further guide the photocatalytic performances of KN-based family and other similar layered semiconductor materials. KN was formed as a secondary phase caused by the volatilization of alkali metal ions, when preparing the K0.5Na0.5NbO3 film in our previous study[33] This phenomenon frequently occurs in the preparation of ferroelectric KNbO3 and KxNa1−xNbO3 based ceramic and film[34,35,36]. It is believed that the present work could be helpful in deeply understanding the intrinsic features of KN and developing potential multifunctional KN-based applications
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