Moisture-Stable CsSnBr₂Cl Halide Perovskite: Electrochemical Insights in Aqueous Environments

In this investigation, moisture-stable CsSnBr 2 Cl nanoparticles were synthesized by incorporating Cl into CsSnBr 3 halide perovskite using the hot injection method. Various analyses including XRD, XPS, UV–vis absorbance, photoluminescence, and Mott–Schottky have confirmed that the structural properties, chemical states, optical properties, and electronic band structure of CsSnBr 2 Cl nanoparticles remain intact even after 75 days of water immersion, thereby conclusively demonstrating their moisture stability. In a three-electrode system, the comparative electrochemical performance of pristine CsSnBr 3 nanoparticles and moisture-stable Cl-incorporated CsSnBr 2 Cl nanoparticles was evaluated in various aqueous electrolytes, including HCl, Na 2 SO 4, and KOH. The results indicate that the CsSnBr 2 Cl electrode material exhibits superior electrochemical properties, such as a larger integrated cyclic voltammetry (CV) area, a wider potential window, longer charge–discharge times, and lower impedance parameters compared to the pristine CsSnBr 3 nanoparticles. The electrochemical performance of CsSnBr 2 Cl nanoparticles was evaluated for potential applications in batteries, supercapacitors, fuel cells, and water splitting, with a focus on reaction kinetics, charge storage mechanisms, and impedance parameters. The electrochemical properties of the nanoparticles were assessed using a three-electrode configuration across various 0.5 M aqueous electrolytes (HCl, Na 2 SO 4, and KOH). In HCl, the nanoparticles demonstrated impressive charge storage capability, achieving a capacitance of 474 F g –1 at 1 A g –1, affirming their suitability for energy storage devices. In Na 2 SO 4 (aq.), the nanoparticles exhibited excellent stability for supercapacitors, operating up to 1.6 V without significant oxygen evolution. Notably, in KOH, they demonstrated potential as effective water-splitting electrodes. The practical applicability of the nanoparticles was evaluated using a symmetric two-electrode configuration with HCl and Na 2 SO 4 electrolytes. The capacitance values were 117 F g –1 in HCl and 70 F g –1 in Na 2 SO 4 at 1 A g –1 . Notably, after 5000 GCD cycles in HCl(aq.), the nanoparticles retained 93% of their capacitance and maintained 91% Coulombic efficiency. They also demonstrated stable operation across a temperature range of 3 to 60 °C, achieving an energy density of 5.83 W h kg –1 at a power density of 600 W kg –1 . This study emphasizes the considerable potential of CsSnBr 2 Cl nanoparticles in advancing electrochemical energy storage technologies and sets a solid foundation for future research and development in metal halide perovskites.