Orthorhombic niobium pentoxide (T-Nb2O5) offers high capacitance and fast charging–discharging rate capabilities when used as an electrode material for Li-ion capacitors. A homogeneous distribution of T-Nb2O5 nanoparticles in a highly conductive matrix represents a promising approach to maximize its energy and power densities. Here we report a one-step CO2 oxidation of two-dimensional (2D) Nb2CTx, a member of the MXenes family of 2D transition metal carbides, which leads to a hierarchical hybrid material with T-Nb2O5 nanoparticles uniformly supported on the surface of Nb2CTx sheets with disordered carbon. The oxidation temperature, duration, and CO2 flow rate determine the T-Nb2O5 crystallite size as well as the structure, composition, and the charge storage properties of the hybrid material. Fifty micrometer thick electrodes of the hybrid material exhibit high capacitance (330 C g–1 and 660 mF cm–2 at a charge–discharge time of 4 min) and good cycling performance in a nonaqueous lithium electrolyte. The charge storage kinetics are dominated by a surface-controlled process. The observed electrochemical performance is attributed to the intrinsic pseudocapacitive response and excellent energy storage capability of T-Nb2O5 coupled with the fast charge transfer pathways provided by the conductive 2D Nb2CTx sheets and the as-formed disordered carbon.

•Highly transparent ruthenium oxide/poly(3,4-ethylenedioxythiophene): poly(styrene-4-sulfonate), (RuO2/PEDOT:PSS) hybrid thin films have been successfully fabricated.•The hybrid thin film shows remarkably high transparency (93%), high conductivity (σDC =279 S/cm), excellent volumetric capacitance (CV =190 F/cm3) and areal capacitance of C/A=1.2 mF/cm2.•Transparent, flexible devices have been fabricated with excellent electrochemical performances, such as C/A=0.84 mF/cm2 and 100% capacitance retention over 10,000 charge/discharge cycles.•Large-area transparent supercapacitor device has been built.Transparent, conductive electrodes are important in many applications such as touch screens, displays and solar cells. Transparent energy storage systems will require materials that can simultaneously act as current collectors and active storage media. This is challenging as it means improving the energy storage capability of conducting materials while retaining transparency. Here, we have used aerosol-jet spraying strategy to prepare transparent supercapacitor electrodes from ruthenium oxide/poly(3,4-ethylenedioxythiophene): poly(styrene-4-sulfonate), (RuO2/PEDOT: PSS) hybrid thin films. These films combine excellent transparency with reasonably high conductivity (DC conductivity =279 S/cm) and excellent volumetric capacitance (CV =190 F/cm3). We demonstrate electrodes with historical high transparency of 93% which display an areal capacitance of C/AC/A=1.2 mF/cm2, significantly higher than the rest reported electrodes with comparable transparency. We have assembled flexible, transparent, solid-state symmetric devices which exhibit T  =80% and C/AC/A=0.84 mF/cm2 and are stable over 10,000 charge/discharge cycles. Asymmetric solid-state device with RuO2/PEDOT: PSS and PEDOT: PSS thin films as positive and negative electrodes, respectively, display an areal capacitances of 1.06 mF/cm2, a maximum power density (P/A)(P/A) of 147 μW/cm2 and an energy density (E/A)(E/A) of 0.053 μWh/cm2. Furthermore, large area transparent solid-state supercapacitor device has been built. We believe the solution-processed transparent films could be easily scaled-up to meet the industrial demands.The aerosol-jet spraying of blended dispersion results in RuO2/PEDOT: PSS hybrid thin film, which explores the synergistic effects of high DC conductivity and low optical conductivity of PEDOT: PSS, coupled with high pseudocapacitance from RuO2 nanoparticles. Consequently, the hybrid thin films demonstrate excellent transparency and areal capacitance in transparent, flexible, solid-state supercapacitors.

Hydrous RuO2 nanoparticles have been uniformly deposited onto nitrogen-enriched mesoporous carbons (NMCs) via a facile hydrothermal method. The nitrogen doping in the carbon framework not only provides reversible pseudocapacitance but also guides uniform deposition of RuO2 nanoparticles. As a result, an extremely high specific capacitance of 1733 F/g per RuO2, comparable to the theoretic capacitance of RuO2, is reached when 4.3 wt % of RuO2·1.25H2O is loaded onto the NMCs. Systematic studies show that either nitrogen-free or excess nitrogen doping result in RuO2 clusters formation and worsen the electrochemical performances. With intermediate nitrogen and RuO2 content (8.1 wt % N, 29.6 wt % of RuO2·1.25H2O), the composites deliver excellent power performance and high specific capacitance (402 F/g) with reversible capacitive response at 500 mV/s. The unique properties of nitrogen in textual, morphological, and electrochemical aspects may also provide further understanding about the effects of nitrogen doping and metal oxide deposition on supercapacitor performance.Keywords: high power performance; hydrothermal method; nitrogen-enriched mesoporous carbon; pseudocapacitor; ruthenium oxide;