N, P co-doped porous graphene with high electrochemical properties obtained via the laser induction of cellulose nanofibrils

Cellulose and its derivatives are natural materials with high carbon contents, but it is challenging to convert their carbon into high value-added carbonaceous materials (e.g., graphene). Here, an approach to convert the carbon in cellulose into N, P co-doped porous graphene (LIG) materials via laser induction is proposed. Cellulose nanofibrils (CNFs), a cellulose derivative with high dispersion uniformity and abundant surface hydroxyl groups, were easily formed on a bulk substrate (thickness ≥5 mm) containing ammonium polyphosphate (APP). Then, a 10.6 μm CO₂ laser was used to scribe for 1–5 passes on the CNFs/APP substrate under an ambient environment to produce N, P co-doped porous LIG. Upon increasing the number of laser scribing passes, the I_G/I_D of LIG first increased and then decreased, reaching a maximum of 1.68 at 4 passes. The good pore structure and low resistance also showed that 4 laser passes were ideal. Besides, the N, P co-doped LIG also showed excellent electrochemical performance, with a specific capacitance of 221.4 F⋅g⁻¹ and capacitance retention of 89.9%. This method exploits the advantages of nanocellulose and overcomes the difficulties associated with directly compounding cellulosic materials, providing a method for the further development of biomass nanomaterials.