A simple, economical, and quick electrochemical deposition of rare-earth metal ion–doped ZnSe/FeS2 double-layer thin films with enhanced photoelectrochemical performance

Abstract

Herein, various rare-earth metal (Eu, Gd, and Sm) ion-doped ZnSe/FeS2 double-layer thin films were deposited on an ITO plate via a quick and facile electrochemical deposition (ECD) method. X-ray diffraction (XRD) studies confirmed that the fabricated double-layer thin films exhibited sharp diffraction peaks which indicate their well crystalline nature. Scanning electron microscopy (SEM) showed that the double layer of ZnSe/FeS2 films was well deposited on the ITO substrate. The electron paramagnetic resonance (EPR) spectra indicated one weaker peak center at 335 mT and one high-instance very sharp peak center around 157 mT for the different metal-doped ZnSe/FeS2 double-layer thin films. From the Raman spectra, it was found that a broad peak centered at 2778 cm−1, which revealed the characteristic vibration of the ZnSe/FeS2 double layer. Electrochemical impedance spectroscopy (EIS) suggested that the Gd3+-doped ZnSe/FeS2 sample possesses a lower charge transfer resistance (Rct) of 39 Ω when compared with Eu3+- and Sm3+-doped ZnSe/FeS2 samples, demonstrating the excellent conductivity of Gd3+-doped ZnSe/FeS2 films. Moreover, the photoelectrochemical study indicates that the Gd3+-doped ZnSe/FeS2 thin film displayed a higher photocurrent than the other samples. This higher photocurrent of Gd3+-doped ZnSe/FeS2 films is mainly owing to its efficient charge separation efficiency to produce more photo-excited electron-hole pairs. Therefore, the attained Gd3+-doped ZnSe/FeS2 double-layer thin film is a promising material for photoelectrochemical device application.