Synthesis and morphology of Ba(OH)2 flakes governing phase-dependent electrochemical performance

• Synthesized flake-like Ba(OH) 2 using a surfactant-assisted method at 80 °C. • Amorphous Ba(OH) 2 flakes undergo phase transition into cubic barium oxide (Fm-3m). • Pristine Ba(OH) 2 flakes exhibit a superior capacitive performance. • Superior performance is caused by preserved hydroxide-derived pseudocapacitance. Barium plays a critical role in a wide range of technologies, from barium titanate-based dielectrics to specialty glass, phosphors, and radiation shielding. Unlike extensively studied barium-based oxides, Ba(OH) 2 is not thoroughly explored as an electrocatalyst or energy storage material, and its intrinsic hydroxide chemistry remains under-investigated. In this study, Ba(OH) 2 flakes are synthesized using a surfactant-assisted method at a low temperature (80 °C), providing a simple route to obtain uniform architectures. X-ray diffraction and X-ray photoelectron spectroscopy analyses confirm that amorphous Ba(OH) 2 flakes undergo a phase transition into cubic barium oxide (Fm-3m) when annealed at 500 °C. Electrochemical evaluations including Tafel analysis and chronopotentiometry demonstrate excellent oxygen evolution reaction activity. Supercapacitor measurements reveal that pristine Ba(OH) 2 flakes exhibit a superior capacitive performance compared with their annealed counterparts, which can be attributed to preserved hydroxide-derived pseudocapacitance. These findings indicate that morphology- and phase-engineered Ba(OH) 2 are a versatile platform for advancing alkaline electrocatalysis and aqueous supercapacitor applications.