Dry-Etched Oxide Templates Enable Scalable and Waste-Free Synthesis of Graphene-Based Aeromaterials

Template-assisted synthesis is widely used to fabricate ultralight carbon aeromaterials, yet conventional wet-chemical template removal requires multistep solvent exchange and critical point drying, which limits scalability, reproducibility, and environmental efficiency. Here, we introduce a dry-chemical template-removal process using forming gas (H₂/N₂) as a liquid-free, furnace-based alternative and evaluate it using graphene-coated tetrapodal ZnO as a representative oxide-templated aeromaterial system. Thermogravimetric and calorimetric analyses identify temperature-dependent reaction regimes, including hydrogen-driven reduction, vapor-transport-limited zinc evaporation, and carbothermic reduction at elevated temperatures, which collectively govern pore opening and wall thinning within the graphene shell. Etching temperatures of 800-1000 °C produce architectures with high structural integrity, whereas higher temperatures further increase porosity but introduce additional defects. Mechanical and mechanoelectrical testing show that dry-etched aeromaterials retain the elastic compliance of wet-etched references while exhibiting up to 4-fold higher electrical conductivity, attributed to thermally enhanced interflake coupling and removal of residual adsorbates. Because zinc is released in vapor form, the method also offers prospects for material recovery and circularity. Overall, gas-phase template removal provides a scalable and environmentally efficient pathway for producing high-performance graphene-based aeromaterials.