Palm oil shell-derived SiO₂/hard-carbon-like nanocomposites for a potential application as dual carbon battery electrode

Palm oil shell waste was converted into SiO₂/hard-carbon-like (HC-like) nanocomposites for a dual carbon Na-ion battery through a one-step air pyrolysis process. Heating the shells for 5 h at 400–1000 °C (5 °C min⁻¹) generated hierarchical porosity with BET surface areas of 570–650 m² g⁻¹. X-ray diffraction and elemental mapping confirmed amorphous HC-like carbon intermixed with SiO₂ nanodomains, while XPS and Raman spectroscopy (D ≈1350cm⁻¹, G ≈1590cm⁻¹; weak 2D ≈2700cm⁻¹) tracked temperature-dependent bond ordering. The electrode prepared from biomass pyrolyzed at 700 °C exhibited the highest specific capacitance (137.0 F g⁻¹), whereas the highest ion diffusion coefficient was observed for the 550 °C sample (5 × 10⁻¹³ cm² s⁻¹). Electrochemical performance indicated rapid Na⁺ ion transport at 550 °C and 700 °C, suggesting these as optimal processing temperatures to balance material structure and electrode performance. This study demonstrates that palm oil shells are a sustainable and high-performance precursor for sodium-ion battery anodes.