Ag3PO4/carbon nanotubes/Ni film electrodes: photoelectrocatalytic properties and mechanism of rhodamine B degradation under an applied negative bias

Ag3PO4/CNTs/Ni composite thin film electrodes were prepared using electrochemical co-deposition. The surface morphology and structural properties of the electrodes were characterized using scanning electron microscopy (SEM), X-ray diffraction, and Raman and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). SEM showed that spherical Ag3PO4 nanoparticles (average diameter of 20-30 nm) were distributed uniformly on the outermost layer of the composite film when the fabrication process was optimized. The inner layer consisted of a network structure that contained interlaced Ag3PO4 and CNTs. The photoelectrocatalytic (PEC) activity and stability of the thin films were investigated by following the degradation of rhodamine B (RhB) at a negative bias under visible light irradiation. At an optimum negative bias of - 0.10 V, the efficiency of PEC degradation of RhB was 2.74 times greater than that observed when a Ag3PO4/Ni thin film was used. Importantly, the Ag3PO4/CNTs/Ni composite films exhibited a synergistic photoelectric effect and PEC stability, and could be reused five times without any significant decrease in the catalytic activity of the film. A reaction mechanism for the PEC degradation of RhB at negative bias by the Ag3PO4/CNTs/Ni thin films was proposed.