Role of sulfur and phosphorous doping on the electrochemical performance of graphene oxide-based electrodes

Heteroatom doping of graphene oxide (GO) with phosphorous (P), and sulfur (S) was studied. In-situ grown binder-free electrodes of these doped and un-doped GO systems were developed via hydrothermal process. S-GO, P-GO, PS-GO, and un-doped hydrothermally treated GO (H-GO) electrodes were thoroughly investigated through physical and electrochemical characterization. The PS-GO electrode, comprising P (10.90 at%), S (0.3 at%), C (45.54 at%), O (36.36 at%), and Ni (2.38 at%) atoms, exhibited a mixed morphology of a few hundred nanometers doped GO flakes and dissolved Ni foam nanorods. Electrochemical analysis showed, this mixed morphology stimulates the charge storage ability of the PS-GO electrode and achieved a high specific capacity of 1218 C/g, compared to 647 C/g for H-GO at 1 mV/s. Electrochemical analysis revealed, charge was primarily stored through the capacitive charge storage mechanism, where only surface atoms are solely responsible for developing a double layer or facilitating redox reactions between electrode atoms and electrolyte ions. Additionally, the PS-GO electrode demonstrated an energy density of 76.94 Wh/kg at 1 A/g, which is much closer to that of batteries. We anticipate that PS-GO has the potential to be utilized as electrode material in modern energy storage devices.