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• A hybrid electrode made of (TEAPW12) and activated carbon (AC) outperforms AC in a high-V organic electrolyte supercapacitor • The inorganic cluster undergoes multi-electron reactions in the hybrid material, even in an aprotic organic electrolyte. • Volumetric capacitance increases by ~36% with polyoxometalates hybridization without sacrificing voltage window. • We are demonstrating for the first time the effective use of polyoxometalates in aprotic electrolyte supercapacitors. Polyoxometalates (POMs) have been shown to work as faradaic additives to activated carbon (AC) in acidic aqueous electrolytes. Yet, their use in organic media allows not only for added capacity but also higher voltage. Here we show that the tetraethylammonium derivative of phosphotungstate [PW 12 O 40 ]3− (PW12) can be homogeneously distributed throughout the pores of activated carbon (AC) in organic solvents such as N,N'-dimethylformamide (DMF) and demonstrate the use of this hybrid electrode material in an organic electrolyte (1 M TEABF4 in acetonitrile) supercapacitor. Our results show the efficient electroactivity of the PW12 cluster even in the absence of protons, providing a higher voltage than aqueous electrolytes and fast and reversible redox activity. The hybrid material shows a combination of double-layer (AC) and redox (PW12) capacities leading to an increase (36%) in volumetric capacitance with respect to pristine AC in the same organic electrolyte (1 M TEABF4 in acetonitrile). Remarkably, we were able to quantify this increase as coming predominantly from non-diffusion-limited processes thanks to the utterly dispersed nature of POMs. Moreover, the hybrid material delivers a good rate capability and excellent cycle stability (93% retention of the initial capacitance after 10,000 cycles). This study has a profound significance on improving capacitance of carbon-based materials in organic electrolytes. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Three dimensional carbon materials with hirerarchically porous structure could exhibit superior energy storage performance than two dimensional stacked carbon nanosheet materials. In this work, we prepared a novel ZIF-8-derived nitrogen doped carbon nanoparticles/graphitic carbon nitride composite electrode material with high electrochemical energy storage performances, including high specific capacitances (495 F g −1 at 0.1 A g −1 and 188 F g −1 at 20 A g −1 ) and a stable cycling durability with no capacitance declination after 5000 charge-discharge cycles in three-electrode system. When assembled as electrode materials in symmetrical two-electrode system, the as-prepared composite electrode material could exhibit high specific capacitances of 349.7 F g −1 at 0.5 A g −1 and 261.2 F g −1 at 5 A g −1 . Accordingly, a high energy density of 11.89 Wh/kg can be achieved at the power density of 247.40 W kg −1 . The improvement stems from its hierarchically porous structure with dominant pore sizes at 3 nm and among 4–40 nm, as well as high exposed pyridinic nitrogen (8.58 at%) and pyrrolic nitrogen (3.59 at%) active sites caused by the insertion of ZIF-8-derived nitrogen doped carbon nanoparticles between g-CN layers. This study has provided a new idea on the design of graphitic carbon nitride nanostructures with improved doping level and hiearchically porous structure. [ABSTRACT FROM AUTHOR]

Two dimensional heteroatoms-doped graphitic carbon electrode materials could exhibit better capacitive properties than undoped carbon materials. However, since the configuration and the content of the heteroatoms as well as their porous structure are difficult to control, the improvement of their energy storage performance is limited. Here, we report a hierarchically porous boron-doped graphitic carbon nitride nanosheet electrode material with high electrochemical energy storage performances, including high specific capacitances at a fast, carbon-like speed (620.0 F g −1 at 0.1 A g −1 and 312.0 F g −1 at 20 A g −1 ), a high energy density of 86.1 Wh kg −1 and a stable cycling durability with no capacitance declination after 2500 charge-discharge cycles. The improvement stems from the hierarchically porous structure with dominant pore sizes among 1–3 nm, increased pyrrolic nitrogen (11.12 at%) and boron (8.21 at%) active sites due to the addition of ionic liquid. This study has provided a new idea on improving the doping level and porous structure of the electrode material by using ionic liquid as both the heteroatoms source and pore template. [ABSTRACT FROM AUTHOR]