Assembled Melamine-Regulated Synthesis of Uniform Manganese Dioxide Nanoribbons for Superior Heating Effect

We report a hydrothermal strategy to synthesize uniform manganese dioxide (MnO₂) nanoribbons using melamine as both a self-assembling template and a mild reducing agent. Melamine self-assembles into a two-dimensional melamine-cyanuric acid (MCA) supramolecular network that directs the growth of MnO₂ nanoribbons, and its partial oxidation (by permanganate) facilitates the nanoribbon formation. Systematic experiments confirm that melamine is essential for obtaining the nanoribbon morphology, and factors such as hydrothermal temperature, reaction time, and reactant concentrations significantly influence the outcome. The as-prepared MnO₂ nanoribbons exhibit strong photosensitivity and a rapid photothermal response, reaching an equilibrium temperature of ∼101.4 °C under one-sun illumination in 60 s. When incorporated as the conductive filler in an electrothermal coating, a small loading of MnO₂ nanoribbons (0.5 wt %) achieves rapid and uniform Joule heating up to 147.3 °C at a low DC bias of 8 V─much higher than a similar coating prepared with MnO₂ nanoparticles synthesized without melamine. The nanoribbon-based coating maintained a stable equilibrium temperature over 10 on/off cycles, demonstrating excellent thermal stability. Furthermore, a composite of the nanoribbon coating with a polyester (PET) film could melt an ice particle within 30 s and completely evaporate it within 120 s at 8 V. These results indicate that MnO₂ nanoribbon-based electrothermal coatings are promising for efficient low-voltage indoor heating and outdoor deicing applications.