The present work reports for the first time a one-step hydrothermal synthesis of ternary-doped (N, S, and P) reduced graphene oxide (rGO) under acidic pH conditions (NSPrGO2-12) using thiamine pyrophosphate (TPP) as both a reducing agent and a single source N, S, and P doping agent under mild experimental conditions. The change in pH of the reaction mixture from acidic (similar to 2.2) to basic (similar to 8.5) creates a change in the surface chemistry of rGO, resulting in TPP-functionalized rGO with modified morphology, structure, surface area and electrochemical performance. This change has been analyzed in terms of the different interactions between the graphene oxide functional groups and various functionalities of TPP at different pH conditions. Under acidic pH conditions, the sample had a crumpled sheet morphology with wrinkles on its surface having interconnected network and possessing a relatively large surface area. Meanwhile, under basic pH conditions, the sample exhibited stacked layer-by-layer sheets that formed an aggregated network-like structure with a smaller surface area. NSPrGO2-12 delivers a high specific capacitance (C-s) value of 269 F/g at 20 A/g with long cyclic stability (93% retention after 5000 cycles at 20 A/g), high coulombic efficiency (100%) and high energy/power density (23.55 Wh/kg/7923.4 W/kg) in an aqueous electrolyte. Moreover, the C-s value of the ternary-doped rGO is significantly higher than its mono-and co-doped counterparts under similar experimental conditions. These features clearly demonstrate the tremendous potential of NSPrGO2-12 as an electrode material for energy storage applications.