A versatile route to metal oxide nanoparticles impregnated in carbon matrix for electrochemical energy storage

•A versatile strategy with high universality is proposed to synthesize metal oxide/carbon composites.•Homogeneous organic/inorganic interface assists construction of metal oxide nanoparticles impregnated in carbon matrix.•The as-prepared composites exhibits impressive potassium ion storage performances. Metal oxide/carbon (MO/C) composites with an intimate coupling MO/C interface structure are promising electrode materials for electrochemical energy storage devices because of their valuable synergistic effects and structural stability. However, the existing synthetic routes could not fully meet the needs of versatile design and synthesis of MO/C composites with controllable structure. Here we propose a general synthetic strategy for versatile synthesis of various MO/C composites composed of metal oxide nanoparticles tightly impregnated in the carbon matrix. The utilization of polydopamine with excellent adhesive and coating capability allows an in situ and confined reaction to form metal ion–polydopamine inorganic–organic hybrid on various substrates, which can be converted to MO nanoparticles intimately embedded in carbon framework after a carbonization treatment. The present synthetic strategy is highly versatile for incorporating various MO nanoparticles, such as Fe2O3, CoO, NiO, Mn3O4, MoO2, VOx, into the carbon matrix with diverse dimensions (e.g., 1D hollow rod, 2D sheet, and 3D network) through employing different substrates. Profiting from the well-organized structure, the resulting MO/C composites exhibit extraordinary potassium ion storage performance when used as anode materials of potassium ion battery. The proposed strategy provides a facile and versatile avenue for boosting the development of advanced carbon-based functional materials for catalysis and other energy storage fields besides potassium ion battery.