Fabrication and evaluation of phosphorus-doped laser-induced graphene with tunable defects and enriched active sites for high-performance supercapacitors

Abstract

Laser-induced graphene (LIG) has garnered substantial consideration in applications based on energy storage owing to its economical nature and exceptional performance as a flexible electrode material. This work presents a straightforward method for synthesising phosphorus-doped laser-induced graphene (PLIG). The synthesis comprised the formation of pure LIG, subsequent dispersion of phosphoric acid via the drop-casting technique, and re-irradiation. The multilayer structure of PLIG was confirmed via the ratio of intensities of 2D and G bands in the Raman spectrum (I_2D/I_G = 0.8). The presence of a peak at 2θ ∼26.07° in X-ray diffraction spectra confirms the formation of graphene. The morphological analysis was done through field emission scanning electron microscopy and high-resolution transmission electron microscopy. The occurrence of P–O and P–C in the P 2p peak's core level spectra in X-ray photoelectron spectroscopy confirms the existence of phosphorus in LIG. Furthermore, the fabricated electrode of PLIG-2 unveiled a remarkable specific capacitance (C_s) of 105 mF cm⁻² at a 2 mV s⁻¹ scan rate, employing a three-electrode system. Moreover, the symmetric supercapacitor device (Swagelok cell) obtained a C_s of 18.6 mF cm⁻² at 0.011 mA cm⁻² current density, and the pouch cell offers 21 mF cm⁻² C_s at 0.05 mA cm⁻² current density, demonstrating its application as an energy storage device.