Computational Analysis of Sn-Based of ZnCu₂SnTe₄, ZnAg₂SnTe₄ and ZnAu₂SnTe₄ Photocatalytic Crystals: DFT Studies, and Adsorption Mechanisms for Methylene Blue Dye

Photocatalysts employ light to speed up chemical reactions such as pollutant breakdown, water splitting, CO₂ collection, and solar energy harvesting. This study investigates how adding other metals (Cu, Ag, and Au) to the Zn-M-Sn-Te framework can boost photocatalytic activity. DFT simulations were used to study the electrical and optical characteristics of three ternary compounds: ZnCu₂SnTe₄, ZnAg₂SnTe₄, and ZnAu₂SnTe₄. Additionally, Monte Carlo simulations were utilized to investigate dye adsorption on these materials. The GGA-PBE functional was discovered to be the most effective at predicting the characteristics of these compounds. Notably, the calculated band gaps using the GGA-PBE functional were resulted to be 1.041 eV, 1.103 eV, and 0.742 eV for ZnCu₂SnTe₄, ZnAg₂SnTe₄, and ZnAu₂SnTe₄, respectively. Subsequently, GGA with PBE has used to calculate the Density of States (DOS), Partial Density of States (PDOS), calculation of effective masses and optical properties. As a result, ZnAu₂SnTe₄ exhibited the lowest band gap, maximum conductivity, refractive index, effective hole mass in relation to effective electron mass, and electron density, showing remarkable photocatalytic capabilities. Next, ZnAg₂SnTe₄ and ZnAu₂SnTe₄ had the lowest adsorption energy with dye molecules, indicating high photocatalytic effectiveness. In addition, ZnAg₂SnTe₄ had the lowest loss function value and reduced reflectance. These findings highlight the materials’ potential value for dye degradation from wastewater, among other applications.