Low‐Voltage Synergistic Thermal Conductivity of Wood‐Based Graphene Composite Electrothermal Films

To address the limitations of conventional low‐voltage electric heaters in achieving high saturation temperatures and rapid electrothermal response, this study presents a high‐performance composite film of graphene nanoplatelets (GNP)/multiwalled carbon nanotubes (MWCNT) with a three‐dimensional conductive network, fabricated via a layer‐by‐layer coating and hot‐pressing process, utilizing pretreated natural wood veneer with enhanced hydroxyl group exposure as a sustainable substrate. Thermochemical and microstructural analyses reveal that a 1:1 GNP/MWCNT mass ratio optimizes the synergistic effect, where MWCNT bridges GNP layers to establish a continuous conductive pathway, reducing interfacial resistance and enhancing thermal transport. The resultant composite film with four coating layers (thickness: ~120 μm) exhibits exceptional electrical conductivity (2000 S·m −1 ) and rapid Joule heating response (2 s), achieving a saturation temperature of 66.1°C–67.9°C under 4 V applied voltage. Cyclic stability tests confirm consistent performance over 3600 s at 4 V, with minimal temperature fluctuations. Furthermore, infrared thermography demonstrated uniform heat distribution (Δ T < 3°C across the surface) and superior heating rates (66°C in 40 s) compared to traditional resistance wire films. This scalable approach offers potential for eco‐friendly, high‐efficiency electrothermal materials in decorative applications.