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

In this investigation, moisture-stable CsSnBr₂Cl nanoparticles were synthesized by incorporating Cl into CsSnBr₃ 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 CsSnBr₂Cl 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 CsSnBr₃ nanoparticles and moisture-stable Cl-incorporated CsSnBr₂Cl nanoparticles was evaluated in various aqueous electrolytes, including HCl, Na₂SO₄, and KOH. The results indicate that the CsSnBr₂Cl 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 CsSnBr₃ nanoparticles. The electrochemical performance of CsSnBr₂Cl 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, Na₂SO₄, 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 Na₂SO₄(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 Na₂SO₄ electrolytes. The capacitance values were 117 F g^-1 in HCl and 70 F g^-1 in Na₂SO₄ 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 CsSnBr₂Cl nanoparticles in advancing electrochemical energy storage technologies and sets a solid foundation for future research and development in metal halide perovskites.