High surface area carbon with a nitrogen content of 7.0% is derived from MOF via in situ g-C3N4 formation. The material shows excellent ORR activity with an onset potential of 0.035 V (vs. Hg/HgO) in alkaline medium apart from high durability and strong disinclination towards methanol crossover.

Carbon dioxide reduction into useful chemical products is a key technology to address urgent climate and energy challenges. In this study, a nanohybrid made by Co3O4 and graphene is proposed as an efficient electrocatalyst for the selective reduction of CO2 to formate at low overpotential. A comparison between samples with different metal oxide to carbon ratios and with or without doping of the graphene moiety indicates that the most active catalyst is formed by highly dispersed and crystalline nanocubes exposing {001} oriented surfaces, whereas the nitrogen doping is critical to obtain a controlled morphology and to facilitate a topotactic transformation during electrocatalytic conditions to CoO, which results in the true active phase. The nanohybrid made up by intermediate loading of Co3O4 supported on nitrogen-doped graphene is the most active catalyst, being able to produce 3.14 mmol of formate in 8 h at −0.95 V vs SCE with a Faradaic efficiency of 83%.

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Here, we report synthesis of a 3-dimensional (3D) porous polyaniline (PANI) anchored on pillared graphene (G-PANI-PA) as an efficient charge storage material for supercapacitor applications. Benzoic acid (BA) anchored graphene, having spatially separated graphene layers (G-Bz-COOH), was used as a structure controlling support whereas 3D PANI growth has been achieved by a simple chemical oxidation of aniline in the presence of phytic acid (PA). The BA groups on G-Bz-COOH play a critical role in preventing the restacking of graphene to achieve a high surface area of 472 m(2)/g compared to reduced graphene oxide (RGO, 290 m(2)/g). The carboxylic acid (-COOH) group controls the rate of polymerization to achieve a compact polymer structure with micropores whereas the chelating nature of PA plays a crucial role to achieve the 3D growth pattern of PANI. This type of controlled interplay helps G-PANI-PA to achieve a high conductivity of 3.74 S/cm all the while maintaining a high surface area of 330 m(2)/g compared to PANI-PA (0.4 S/cm and 60 m(2)/g). G-PANI-PA thus conceives the characteristics required for facile charge mobility during fast charge-discharge cycles, which results in a high specific capacitance of 652 F/g for the composite. Owing to the high surface area along with high conductivity, G-PANI-PA displays a stable specific capacitance of 547 F/g even with a high mass loading of 3 mg/cm(2), an enhanced areal capacitance of 1.52 F/cm(2), and a volumetric capacitance of 122 F/cm(3). The reduced charge-transfer resistance (RCT) of 0.67 Ω displayed by G-PANI-PA compared to pure PANI (0.79 Ω) stands out as valid evidence of the improved charge mobility achieved by the system by growing the 3D PANI layer along the spatially separated layers of the graphene sheets. The low RCT helps the system to display capacitance retention as high as 65% even under a high current dragging condition of 10 A/g. High charge/discharge rates and good cycling stability are the other highlights of the supercapacitor system derived from this composite material.

Developing nonprecious metal-based electrocatalysts to convert water into green fuels (H2 and O2) is key to address urgent climate and energy challenges. We have prepared an electrocatalyst by the immobilization of NiCo2O4 on a phosphazene-based covalent organic polymer (P-COP) through a facile hydrothermal method. The elemental composition of the P-COP showed the presence of a greater amount of heteroatoms N (6.62%) and P (5.62%) throughout the polymer support. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were utilized to determine the atomic structure of the nanocuboids, which depicted the formation of an inverse spinel structure. A NiCo2O4-P-COP-based electrode was simultaneously used for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), and it displayed a minimum overpotential of 270 and 130 mV (V vs RHE), respectively, at a current density of 10 mA cm–2. In addition, it acted as an oxygen reduction catalyst with a half-wave potential of 0.83 V (V vs RHE) and a maximum current density of 4.5 mA cm–2. The electrocatalytic activity is comparable with that of the commercially available Pt and RuO2 catalysts. The combined experimental and computational studies confirm that the catalytic centers formed through the interaction between the heteroatoms (N and P) in the phosphazene matrix and metal oxides (Co and Ni) play an important role in its improved durability and electrocatalytic activity.

Organic−inorganic hybrid polymeric materials have shown potential applications in various fields. An approach to prepare a new class of a covalent organic−inorganic hybrid polymer (COIHP-1) using tris (2,3,6,7,10,11-hexahydroxytriphenylene) and inorganic heterocycle (hexachlorophosphazene) is developed. The design of COIHP-1 with porous nature has been an important goal as it can fulfill the demands of next-generation batteries and other electrochemical devices. COIHP-1 shows a high electrical conductivity of 9.52 × 10 −3 S/cm. For the first time, COIHP-1 is employed as an anode material with maximum capacity in Na + batteries, and it was characterized by various spectroscopic studies. It delivers a reversible capacity of 310 mAh g −1 at a current density of 0.035 A g −1 , retains 65% of initial capacity after 500 cycles, and preserves the mesoporous nature even after prolonged cycling as proved by the post transmission electron microscopy (TEM) analysis. Moreover, COIHP-1 shows an excellent rate capability: it delivers 90 mAh g −1 even at a high current density of 3 A g −1 . The enhanced Na + storage capability, cycling stability, and rate capability are due to the mesoporous scaffold, which offers reversible accommodation for the ions. Mainly, the Na + storage capability of COIHP-1 arises because of its polymeric −PN− framework layer, which also provides hosting sites for the ions in the π-bond or lone pair of N. This work opens a door for developing a new kind of hybrid polymeric electrode material for rechargeable Na + batteries.

Herein, we have investigated the mode of electrochemical degradation of polyaniline (PANI) when it was utilized as electrodes for supercapacitors. The PANI‐based electrodes in supercapacitor devices were biased at a constant potential of 0.80 V, and the performance characteristics and property changes were carefully investigated as a function of the difference in the polarity of the electrodes. Subsequent to this, the analysis of the individual electrodes [positive (POS‐PANI) and negative (NEG‐PANI)] shows that the degradation mainly occurs at POS‐PANI in comparison to NEG‐PANI. Moreover, NEG‐PANI retains a maximum capacitance of 510 F g−1, with a low charge‐transfer resistance (RCT) of 1.84 Ω and similar redox behavior in comparison to the fresh PANI (f‐PANI). In contrast to this case, POS‐PANI shows significant loss in capacitance (250 F g−1) and increase in RCT (3.5 Ω) with a disappearance of the characteristic redox behavior normally displayed by PANI. Furthermore, the drastic drop in the electrical conductivity for POS‐PANI (1.2 S cm−1) compared to f‐PANI (3.4 S cm−1 and NEG‐PANI (2.4 S cm−1) shows that the degradation of PANI occurs mainly at the anode (POS‐PANI) and, thus, contributes to reduce the net performance of the cell. Hence, to ensure this potential‐induced degradation of PANI in supercapacitors and also to promote the system stability, we made an asymmetric supercapacitor (ASC) by keeping PANI as a negative electrode and using carbon as a positive electrode. The derived system is found to display stable capacitance behavior before and after the potential application, in contrast to the ASC fabricated by using conventional method, that is, by keeping PANI as the positive electrode and carbon as the negative electrode. Furthermore, the durability analysis of the prototype solid‐state ASC shows an enhanced durability of 27 000 cycles with excellent columbic efficiency. The findings of the present study will be helpful in the development of highly stable supercapacitors and other similar energy systems when a material like PANI should be utilized for the electrode applications.

The post-synthetic modification (PSM) of metal-organic frameworks (MOFs) with redox-active molecules under mild conditions is a highly challenging tool to modify the inherent properties of MOFs without altering their crystallinity...