Effect of carbon quantum dots on the photo‐absorption, photo‐response and photoelectrochemical performance of KNb 3 O 8 film photoelectrode

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.