Palladium-mediated interfacial orbital hybridization enables record electrical conductivity in copper/graphene composites

The ongoing trend toward higher integration and power density in modern electronics increasingly exposes the thermal and reliability limits of conventional copper conductors, creating a critical bottleneck restricting further technological progress. Copper/graphene composites have emerged as a promising candidate to overcome these electrical limitations, yet their practical implementation is hindered by weak interfacial adhesion and widespread void formation between the graphene coating and the copper substrate, which cause severe electron scattering and degrade macroscopic conductivity. Herein, we report a palladium-mediated interface engineering strategy for fabricating highly conductive Pd/Gr-Cu composite wires via a scalable surface-coating process. Ultrafine palladium nanoparticles improve the interfacial compatibility between graphene and copper, suppress coating delamination, and promote the formation of a compact conductive interface. The optimized Pd/Gr-Cu composite wire achieves an electrical conductivity of 107.7% IACS, along with reduced temperature coefficient of resistance and enhanced current-carrying capability. Combined experimental characterization and theoretical calculations reveal that the palladium-mediated interface strengthens orbital hybridization and accelerates charge transfer, confirming a dual role in enhancing both mechanical adhesion and interfacial charge transport. This work provides an effective interfacial design strategy for developing high-performance graphene-coated copper conductors.