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Pine needle-derived nitrogen and oxygen co-doped porous carbon can be utilized as high-performance electrodes in zinc-ion hybrid supercapacitors.

Construction of carbon nitride based 3D/0D intramolecular DA catalysts with enhanced optical and electrical properties for efficient photoreduction of CO2.

Enzyme/MOF composites with high activity and stability were synthesized via the pressure-induced-stimulated-aging (PISA) strategy.

This study summarizes the recent advances of functional separators for stable aqueous zinc batteries.

Organic molecules with multi-electron redox-active centers have great potential in the field of electrochemical energy storage. Fixing them on the surface of graphene can increase the pseudo-capacitance by enhancing the electronic interaction. However, the clues about how to screen suitable molecules to modify graphene and the effect of the type of substituents on the capacitive performance of graphene are not clear. In this paper, indole molecules with four different types of substituents (nitro, amino, hydroxyl, methoxy) were selected to modify N-doped graphene (5-NIFGN, 5-AIFGN, 5-HIFGN, 5-MIFGN) by a simple one-step hydrothermal method. Among the selected indole molecules, 5-aminoindole was found to be highly compatible with graphene. 5-AIFGN has the maximum specific capacitance and discharge capacity of 831.5 F g−1 and 277.2 mA h g−1 at 1 A g−1, respectively, and a long cycle life (reaching 91% after 5000 cycles). In further practical application evaluation, the symmetrical device based on the 5-AIFGN electrode achieved an energy density of 38.0–43.4 W h kg−1 and a power density of 800–8000 W kg−1. Our work provides an efficient route for the design of high-performance organic electrode materials by properly designing the structure of organic molecules to enhance their adsorption affinity and electronic interaction with graphene, thus increasing the contribution of pseudo-capacitance.

Fluorination of conjugated polymers has been explored as a viable strategy for enhancing the overall performance of corresponding polymers. In this work, two trifluoromethylated polyindoles (5-PFMIn and 6-PFMIn) are synthesized via simple electropolymerization and applied as energy storage materials for supercapacitors. Spectroscopic, morphological, thermal stability, and electrochemical analyses of trifluoromethylated polyindoles and their non-fluorinated counterparts (5-PMIn and 6-PMIn) are performed to reveal the significant effect of the trifluoromethyl group on the properties of polymers. Compared with non-fluorinated counterparts, 5-PFMIn and 6-PFMIn show rougher morphologies and higher thermal stabilities, and more interestingly, the fluorination of polyindoles results in substantial improvement of their electrochemical behavior. The specific capacitances of 5-PFMIn and 6-PFMIn are found to be 269 F g−1 and 296 F g−1 at 10 A g−1, respectively with excellent cycling stability of about 90% after 5000 cycles, which are superior to those of their counterparts, 5-PMIn (75 F g−1, 73%) and 6-PMIn (178 F g−1, 70%). The promising trifluoromethylated polyindoles demonstrate high potential for electrochemical capacitor application.

Advanced wearable organic electronics have been widely studied for flexible textile-based strain sensors. However, two main issues to be addressed in wearable electronic sensors are the poor electron transfer under tensile conditions and water durability. In this work, we proposed an efficient strategy for the fabrication of a highly conductive commercial textile coated with poly(3,4-ethylenedioxythiophene) (PEDOT) via vapor phase polymerization (VPP) as a wearable thermoelectric (TE) strain sensor. The PEDOT-coated textile exhibited excellent mechanical elasticity and electrical properties in response to external strain. More importantly, the strain sensor showed a good strain after cyclic loading of an external stress. Moreover, the as-fabricated PEDOT-coated textiles show superior water durabilities due to the robust PEDOT coatings on the textiles through the in situ polymerization process. A large output voltage of 5.0 mV was achieved at a temperature gradient (ΔT) of 25 K, which is promising for textile generator applications. An optimized gauge factor (GF) of the strain sensor reached 54 at a strain of 1.5%, which has the capability to fully satisfy the demands of wearable electronic sensor devices.

Freestanding flexible capacitive materials are ideal for use in bendable electronic devices. However, it is difficult to prepare pure PEDOT films in a freestanding state by chemical and electrochemical methods. Here, we used a simple strategy of introducing alkoxy, ether, ester, and amide chains for bridging two EDOT units to form precursors, which could then be electrodeposited readily to produce freestanding and flexible films. The precursor with the amide group was suitable for obtaining higher-quality films with improved thermal stability, mechanical properties, and capacitive performance. In addition, the asymmetric PBEDTA//PEDOT capacitors exhibited a capacitance retention rate of 98.5% after 5000 cycles, which is higher than those of PBEDTH//PEDOT (92.7%), PBEDTG//PEDOT (80.5%), and PBEDTE//PEDOT (86.8%) capacitors. This result indicates that the polymer films and, in particular, the PBEDTA films, are suitable for use in flexible supercapacitors.

In this work, poly(N-methyl-3,4-dihydrothieno[3,4-b][1,4]oxazine) (PMDTO), a new nitrogen poly(3,4-ethylendioxythiophene) (PEDOT) analogue, was synthesized by an electrochemical deposition method, and the capacitive properties of PMDTO were investigated and compared with those of PEDOT. The structure and morphology of PMDTO were characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermal analysis. The pseudocapacitive properties of the as-prepared PMDTO electrodes have been examined by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) measurements and electrochemical impedance spectroscopy (EIS) in 0.1 mol L−1 CH3CN–Bu4NBF4 electrolyte solution. The as-prepared PMDTO electrode showed a high specific capacitance of 154.3 F g−1 at a discharge current density of 3 A g−1 and exhibited cycling stability with the maximal capacitance retention of nearly 71% after 500 cycles at a high current density of 10 A g−1. Additionally, the asymmetrical supercapacitor based on PMDTO and PEDOT electrodes exhibited a maximum specific capacitance of 63.5 F g−1 and an energy density of 12.7 W h kg−1 at a power density of 0.59 kW kg−1. These results implied that the PMDTO electrode can be used as a potential electrode material for supercapacitors.

For organic thermoelectric materials, a main challenge is to achieve high electrical conductivity and a large Seebeck coefficient, in order to improve the power factor. Here we suggest a simple way to address this issue through the addition of a small amount of liquid-phase exfoliated MoS2 nanosheets into poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) solutions by direct vacuum filtration. The effects of exfoliated MoS2 nanosheets in common organic solvents on the thermoelectric properties of PEDOT:PSS were investigated. The organic solvent-assisted exfoliated MoS2 nanosheet solution was found to play an important role in improving the thermoelectric performance of the PEDOT:PSS thin film. Common organic solvents effectively removed some of the PSS during the formation of the film, resulting in a significantly enhanced electrical conductivity (1250 S cm−1) for the PEDOT:PSS/MoS2 (PM) thin film. On the other hand, the introduction of MoS2 nanosheets in PEDOT:PSS led to a slight increase of the Seebeck coefficient from 14.5 to 19.5 μV K−1 without a significant reduction of the electrical conductivity of the PM thin film. An optimized power factor of 45.6 μW m−1 K−2 was achieved for the PM thin film with 4 wt% MoS2 exfoliated in an N,N-dimethylformamide (DMF) solution. The exfoliated MoS2 nanosheets in DMF exhibited a better effect on the thermoelectric performance of the PM composites than did those in other organic solvents. The method used here suggests a novel strategy for improving both electrical conductivity and the Seebeck coefficient, and hence optimizing the thermoelectric performance of the PEDOT:PSS thin film.

In this work, a high-capacitance hybrid nanocomposite based on reduced graphene oxide (RGO) and polyindole (PIn) was fabricated via an in situ chemical oxidative polymerization approach. The structure and morphology of PIn/RGO were investigated by FT-IR, Raman spectroscopy, SEM and TEM. The electrochemical properties of this electrode in aqueous H2SO4 electrolyte were also investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS). Compared to RGO and PIn electrodes, the PIn/RGO hybrid nanocomposite shows a large improved specific capacitance of 322.8 F g−1 at 1.0 A g−1, good stability with a cycling efficiency of 94.5% after 1000 cycles, and high energy density of 36 W h kg−1 at a high power density of 5000 W kg−1. The enhanced performance is proposed to arise from the synergetic effect between PIn and RGO. In addition, the symmetric PIn/RGO//PIn/RGO supercapacitor showed specific capacitance of 99.8 F g−1 and only 3.7% decay after 1000 cycles. These results imply that PIn/RGO should be a promising electrode material for supercapacitor applications.

Cycling instability of catalysts is a persisting challenge in heterogeneous catalysis. In this work, we reported an effective in situ strategy for preparing ZIF-8 supported carbon-stabilized Pd nanoparticles (C@Pd/ZIF-8). The original ZIF-8 structure was well-preserved after the formation of Pd nanoparticles and amorphous carbon. Here, the Pd nanoparticles were encapsulated in the carbon matrix with a good dispersion. The as-prepared catalysts showed a better activity and cycling stability for the hydrogenation of C[double bond, length as m-dash]C containing substrates. C@Pd/ZIF-8 catalysts are reusable without significant loss of activity after 5 cycles, exhibiting higher cycling stability than those prepared from directly supported Pd nanoparticles on ZIF-8 (Pd/ZIF-8).

Poly(indole-7-carboxylic acid) (PICA) nanowires with conductivity of 5 × 10−2 S cm−1 were prepared by a facile, one-step and template-free electrodeposition method. The hydrogen bond interactions between the N–H group and the carboxyl group facilitated the formation of PICA nanowires. The diameter of the PICA nanowires was about 40 nm confirmed by scanning electron microscopy. Fourier transformation infrared spectroscopy and 1H NMR spectroscopy confirmed that the polymerization occurred at the C2 and C3 position on the indole ring. The electrochemical capacitance properties of the PICA nanowires were investigated with cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscope techniques. A remarkable specific capacitance of 373.2 F g−1 was obtained at a current density of 2.5 A g−1 in 1.0 M H2SO4 solution. PICA nanowires presented an excellent cycle life with 91% specific capacitance retention after 1000 charge–discharge processes. The energy density of the symmetric full cell based on two PICA electrodes was 7.03 W h kg−1 at a power density of 4500 W kg−1. These results implied that the PICA nanowires will be a promising electrode material for supercapacitors.