Publications internationales
Résumé: In this study, Cu2NiSnS4 (CNTS) thin films were synthesized using a novel string pump spray pyrolysis method at varying substrate temperatures (ranging from 300 °C to 410 °C) to evaluate their structural, optical, and photocatalytic properties. X-ray diffraction (XRD) analysis revealed that all CNTS films exhibited a polycrystalline cubic phase with space group , with preferred orientation along the (111) plane. Increasing the substrate temperature led to a shift in XRD peaks toward higher angles, indicating enhanced crystallinity without the presence of impurity phases. X-ray photoelectron spectroscopy (XPS) showed temperature-dependent changes in elemental composition, notably a significant increase in surface oxidation at higher temperatures, particularly for Sn and O, while Ni and S content decreased. EDS analysis confirmed the presence of all four constituent elements of CNTS. Optical absorption measurements revealed that the CNTS films have a high absorbance in the visible range, with an optimal band gap that increases from 1.1 to 1.7 eV as the substrate temperature rises. Photocatalytic experiments under UV irradiation revealed that the films synthesized at 360 °C exhibited the highest photodegradation efficiency, achieving 91.12 % degradation of Brilliant Green dye. The photocatalytic activity followed a pseudo-first-order kinetic model, with the highest rate constant observed for the CNTS film deposited at 360 °C. However, further increases in deposition temperature led to a decline in photocatalytic performance, attributed to increased film thickness and consequent charge carrier recombination. These results highlight the critical role of deposition temperature in optimizing the structural and photocatalytic properties of CNTS thin films.
Résumé: The current study explores the deposition of thin films of pure zinc oxide (ZnO) and molybdenum-doped zinc oxide (Mo:ZnO) using spray pyrolysis, with Mo doping concentrations of 3 %, 5 %, and 7 %. A comprehensive characterization was conducted employing Raman spectroscopy, energy dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, and electrochemical measurements. This multi-faceted approach aimed to investigate the structural, morphological, optical, and chemical composition of the films. Raman spectra were utilized to assess the structural properties, while EDX and XPS analyses confirmed the presence of Zn, O, and Mo in the synthesized samples, with XPS revealing Mo in the +6 oxidation state in Mo-doped ZnO films. Furthermore, UV–Vis absorption spectroscopy, analyzed via Tauc’s relationship, indicated an increase in the band gap from 3.28 eV to 3.35 eV with increasing Mo content. Photocurrent and Mott–Schottky measurements confirm the n-type character of all deposited films and were in good agreement. Analysis by means of cyclic voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and galvanostatic charge–discharge (GCD) reveal an enhancement in specific capacity (SC) for Mo-doped ZnO compered to undoped ZnO with an increase with Mo concentrations. The highest SCs are obtained for 3 % Mo-ZnO film and were found equal to 37.02 and 113 F/g for v: 10 mV/s and IGCD: 0.6 A/g respectively.