Caffeine–stabilized methylammonium lead iodide perovskites electrocatalyst for hydrogen evolution reaction

This study examined the electrocatalytic production of hydrogen gas using caffeine-stabilized methylammonium lead iodide (MAPbI₃) perovskite material. Crystallinity improvement was observed in 2Ɵ = 112 and 141 with the incorporation of caffeine. Additionally, MAPbI₃@Caffeine exhibited relatively stronger thermal stability than either MAPbI₃ or caffeine with a sublimation temperature of 243 °C. Charge transfer at the interface between the electrocatalyst and electrolyte was meticulously analyzed using Electrochemical Impedance Spectroscopy (EIS) whereby Graphite was ∼10.5 kꭥ, then Graphite-Caffeine, Graphite-MAPbI₃, and Graphite-MAPbI₃-Caffeine were ∼5.47, 12.6 and 4.37 kꭥ. Hydrogen production current increased gradually from the onset potentials of about −0.38, −0.29, −0.24 and −0.13 V (vs. RHE) for Graphite, Graphite-Caffeine, Graphite-MAPbI₃, and Graphite-MAPbI₃-Caffeine respectively, and finally approached a maximum at −2.5 V. The comprehensive examination revealed that hydrogen current increased with increasing incorporation of caffeine in the perovskite material. Pure graphite showcased a remarkable TOF of 24.79 s⁻¹, outperforming the modified Graphite-MAPbI₃, which recorded a TOF of 23.87 s⁻¹. In stark contrast, the catalytic performance of Graphite-MAPbI₃-Caffeine was significantly lower, with a TOF of only 6.85 s⁻¹. The graphite electrode demonstrated a noteworthy catalytic activity of 2.077 × 10⁻⁷ mol L⁻¹ s⁻¹, indicating its efficiency in facilitating reactions. In comparison, the modified graphite enhanced with MAPbI₃ exhibited a slightly elevated catalytic activity of 2.082 × 10⁻⁷ mol L⁻¹ s⁻¹, while the MAPbI₃-Caffeine combination exhibited a parallel performance with a catalytic activity of 2.079 × 10⁻⁷ mol L⁻¹ s⁻¹.