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

Abstract The KNb ₃ O ₈ 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 KNb ₃ O ₈ film on FTO glass (SnO ₂ conductive glass doped with fluorine) show that the thin KNb ₃ O ₈ crystals are apt to stack along the [020] direction of KNb ₃ O ₈ crystal structure. Scanning electron microscope and transmission electron microscope results indicate that most of KNb ₃ O ₈ 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 KNb ₃ O ₈ 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 KNb ₃ O ₈ 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.