Delaminated Graphene Nanosheet from Cardboard Using H₃BO₃–Assisted Laser Carbonization for H₂ Generation via NaBH₄ Methanolysis

Laser-induced graphene (LIG) synthesized from polymers (i.e., polyamide) has shown great promise for flexible electronic device applications. However, these polymer substrates are nonreactive, rigid, dense, limiting functionalization, and result in a poorly activated, low-quality LIG with poor physicochemical properties. Additionally, environmental concerns and high costs associated with plastics are problematic. In this study, we utilized waste cardboard as an eco-friendly, low-cost, and reactive substrate to synthesize stable and reproducible boron-doped laser-induced graphene (B-LIG) through H3BO3-assisted laser carbonization. The resulting delaminated B-LIG acts a metal-free catalyst for efficient hydrogen generation via NaBH4 methanolysis. The H3BO3 concentration was adjusted to modulate graphene quality, boron doping levels, and physicochemical properties. B atoms facilitate the graphitization of LIG and boost electron-rich sites that enhance the adsorption of BH4–. Simultaneously, B doping introduces Lewis acid sites that interact with the lone electron pair on the oxygen atom of methanol. This interaction weakens the O–H bond, facilitating its cleavage and promoting hydrogen release in B-LIG, enabling rapid hydrogen generation through NaBH4 methanolysis. As a result, the HGR achieved is 19,330 mL g–1 min–1, with an activation energy of 44.7 kJ mol–1. This study demonstrates how biomass can be effectively converted into high-quality LIG with beneficial properties.