Annealing‐Driven Morphological Evolution of MoS ₂ @α‐MoO ₃ Heterostructures Toward Enhanced Catalysis and Na‐Ion Supercapatteries

This study offers a cost-effective and high-yield electrochemical route for synthesizing molybdenum nanocomposites for energy storage and conversion. MoS₂@α-MoO₃ heterostructure nanomaterials are synthesized using an affordable electrosynthesis method on graphite substrate, followed by a simple annealing process at different temperatures. Then, graphite/MoS₂-amorphous electrodes are annealed at 300 °C, 400 °C, and 500 °C. Following physicochemical characterizations, statistical and morphological analyses, including monofractal and multifractal formalisms are conducted. Findings indicate increasing annealing temperature enhances surface roughness and irregularity with well-developed surface morphology. In a redox-additive electrolyte (1.0 M Na₂SO₄ + 1.0 M NaI), G/MoS₂@α-MoO₃-500||G/rGO Na-ion asymmetric supercapattery and G/MoS₂@α-MoO₃-500||G/MoS₂@α-MoO₃-500 Na-ion symmetric supercapattery are fabricated. The G/MoS₂@α-MoO₃-500||G/rGO supplies a specific capacity of 191.79 mAh g^-1, 45.01 Wh kg^-1 energy density, and 234.72 W kg^-1 power density at 1 A g^-1 with 95.4% retention after 10 000 cycles with a broad potential window of 1.30 V. The G/MoS₂@α-MoO₃-500||G/MoS₂@α-MoO₃-500 demonstrates C_S of 207.13 mAh g^-1, E_s of 48.62 Wh kg^-1, and P_s of 234.72 W kg^-1 at 1 A g^-1 with 96.4% retention after 10 000 cycles. Tailoring developed morphologies at G/MoS₂@α-MoO₃-500 electrode yields catalytically active sites for excellent electrocatalytic activities toward hydrogen evolution reaction (η_{j = 10} = 44 mV and Tafel slope of 81 mV dec^-1) in acidic solution.