Electronic and Optical Properties of Cs₂PtCl₆ and Rb₂PtCl₆ Double Perovskites for Photocatalytic Hydrogen Production

Abstract

Abstract. Water splitting has become the cornerstone of hydrogen production and thus the fundamental process for all clean energy systems. While pure Platinum (Pt) exhibits a high potential for integration into catalytic technologies, the design of efficient, stable, and low cost catalysts remains the major challenge. Alloying Pt or developing new alternative represent a promising pathway toward more sustainable catalysts. In this context, non-toxic halide double perovskites have established as effective materials for energy conversion thanks to their structural stability and tunable optoelectronic charactrestics. The optoelectronic properties of Cs₂PtCl6 and Rb₂PtCl6 were investigated using Density Functional Theory (DFT). The predicted band gaps suggest high light absorption in the visible region, indicating the suitability of the studied compounds for solar-driven water-splitting processes. Additionally, replacing Cs⁺ with Rb⁺ improves charge carrier separation through local lattice distortion and reduces the band gap. These findings show that Cs₂PtCl6 and Rb₂PtCl6 are stable, non-toxic, and tunable choices for photocatalytic hydrogen production and broader energy-harvesting applications.