Non-Epitaxial Growth of Transition Metal Oxide Crystalline Nanorods on Laser-Induced Graphene

Laser-induced graphene (LIG) has driven significant advances in wearable electronics, advanced healthcare, and energy devices. However, achieving diverse functionalities and high-performance for practical use requires integrating functional materials, which remains challenging due to poor synthesis results or complex chemical treatments. Herein, direct, seedless growth of transition-metal-oxide (MO) crystalline nanorods on LIG is demonstrated, even under lattice-mismatch conditions, via a non-epitaxial process. Ultrafast laser pyrolysis during LIG formation introduces nitrogen- and oxygen-containing surface groups that facilitate the nucleation of MO during subsequent synthesis, enabling the selective growth of MO nanorods exclusively on LIG patterns without additional lattice-matching or patterning steps. Through this non-epitaxial growth, crystalline orthorhombic WO₃·0.33 H₂O and β-FeOOH nanorods are successfully synthesized on LIG micro-patterns. As a proof-of-concept, LIG electrodes integrated with these crystalline MO nanorods are employed in all-solid-state micro-supercapacitors, exhibiting significantly enhanced capacitive performance owing to the electrochemical reactivity of the MO nanorods, together with excellent mechanical and cyclic stability. Beyond this demonstration, the non-epitaxial strategy offers a versatile route for harnessing the diverse functionalities of MO nanostructures, unlocking new possibilities in graphene-based electronics.