Effect of carbon quantum dots on the photo‐absorption, photo‐response and photoelectrochemical performance of KNb3O8 film photoelectrode

Abstract

Abstract The KNb3O8 crystals and carbon quantum dots were synthesized via hydrothermal reaction method, their crystal structural and morphological properties were investigated by X‐ray diffraction, scanning electron microscope and transmission electron microscope, respectively. The X‐ray diffraction patterns of KNb3O8 film on FTO glass (SnO2 conductive glass doped with fluorine) show that the thin KNb3O8 crystals are apt to stack along the [020] direction of KNb3O8 crystal structure. Scanning electron microscope and transmission electron microscope results indicate that most of KNb3O8 crystals have a width of about 0.5 μm and a length of more than 5 μm and the carbon quantum dot has a graphite structure with a size of about 3 nm. The UV‐response KNb3O8 thin film electrode was loaded by carbon quantum dots and showed broader photo‐absorption characteristic (up to visible light region) and higher photocurrent (a bias of 0.4 V vs SCE), as compared of the pristine KNb3O8 film electrode. In addition, their photo‐electrochemical (PEC) performances were also investigated under different light irradiation conditions with an applied potential between −0.4 and 0.7 V versus SCE.