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Despite the significant progress in Zn−air batteries (ZABs), their widespread use in the rechargeable sector is hindered due to the scarcity of efficient bifunctional oxygen catalysts that can catalyze both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). To address this, an ORR/OER bifunctional electrocatalyst is designed with ultrafine alloyed FeNi nanoparticles encapsulated in a 3D interconnected N‐ doped carbon network structure, featuring a carbon nitride backbone enclosed in graphitic carbon. The FeNi electrocatalyst (3DFeNiPDC) showed good bifunctional activity toward both ORR and OER in the basic medium with a low overpotential value of 30 mV for ORR and 6 mV for OER compared to its state‐of‐the‐art counterparts Pt/C, and RuO2, respectively. Utilizing 3DFeNiPDC in a rechargeable Zn‐air battery (RZAB) yields an open circuit voltage (OCV) of 1.35 V, a maximum power density of 232 mW cm−2, and an energy density of 707 W h kg−1. Additionally, a flexible RZAB employing 3DFeNiPDC demonstrates an OCV of 1.4 V with various bending angles. These finding suggest 3DFeNiPDC as a viable alternative to noble metal‐based RZABs, offering superior bifunctional electrocatalytic activity and stability, particularly with its enhanced air‐breathing properties facilitating improved operability under practical conditions. [ABSTRACT FROM AUTHOR]

Investigating electrochemical features of proton-conducting organic crystalline materials is relevant in developing efficient energy storage and conversion devices. However, the poor structural flexibility of the crystalline materials at the molecular level often impedes hydrogen bond reorganization of the proton carriers during proton migration, ultimately leading to low ionic conductivity. Here, we report crystals of azobenzene, functionalized with dipicolylamine at both ends (Azo-DPA), which contain an extended hydrogen-bonding network with water molecules in its structure. Interestingly, the crystals display remarkable mechanical flexibility explicitly probed by the nanoindentation technique. The mechanically flexible neutral organic crystals devoid of any acidic moieties (–COOH, –PO3H2, etc.) within the system, exhibit promising proton conductivity (1.63 × 10−4 S cm−1 at 30 °C under 95% relative humidity) which is almost 100 times better compared to the neutral organic systems reported to date. Mechanically flexible redox-active crystalline organic material (Azo-DPA) capable of impressive proton conduction was employed as an electrode material for the first time in an aqueous battery containing Zn2+ ions. The experimental and theoretical studies on the charge storage mechanism revealed the redox activity of the azo (–N＝N–) centers involving reversible insertion/extraction of protons and Zn2+ ions. Ultimately, the electrode displayed a specific capacity ∼49 mA h g−1 with almost 100% retention after 1400 cycles, encouraging the scope of redox-active organic crystalline materials for energy storage applications. [ABSTRACT FROM AUTHOR]

Electrochemical energy conversion and storage systems have an indispensable place in the modern world to fulfill the increasing energy demands. Among the different storage devices, rechargeable zinc–air batteries (ZABs) have become one of the most promising energy technologies owing to the abundance and inexpensiveness of Zn, simple operation, environmental friendliness, and reasonable energy density. However, the sluggishness of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) occurring in ZABs is a serious obstacle in their progress and commercialization. This creates a need for the development of efficient bifunctional electrocatalysts for ORR and OER. Conductive metal–organic frameworks (cMOFs) imbibing the general properties of MOFs, like high surface area, tunable porosity, redox-active centers, and additional intrinsic conductivity, can be a very lucrative option for developing bifunctional ORR and OER electrocatalysts for ZAB applications. In this review, we discuss the conductivity and design strategies of conductive MOFs, the basic configuration of ZABs, and the use of cMOFs for ZAB applications. The future directions for the improvement of cMOFs for ZABs have been provided, which hopefully will incite interest among researchers for further exploring cMOFs for ZABs. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable Zn‐metal batteries (AZMBs) are promising energy storage aids due to their inherent safety, low cost, and competent performance, with prospects in stationary and portable applications. In this regard, one of the critical requirements is developing electrodes that can adapt to mechanical deformation without compromising the charge storage performance. The current work demonstrates the development of a binder‐free and mechanically flexible composite cathode film (VP/fCNT‐F, where 'F' stands for the film) based on VOPO4 (VP) and functionalized carbon nanotubes (fCNTs). The VP/fCNT‐F film processing involves simple vacuum filtration of the composite obtained from the in‐situ reaction of the fCNTs and the VP precursor in an aqueous medium. The functionalization of carbon nanotube (CNT) is important for the homogenous dispersion of VP and fCNT. The VP/fCNT‐F electrode is used as a monolithic electrode in AZMB cells in combination with both liquid and quasi‐solid‐state gel polymer electrolytes. Besides, the utility of the VP/fCNT‐F electrode in a flexible battery configuration is also demonstrated. Interestingly, in both the coin‐cell and flexible configurations, the VP/fCNT‐F electrode delivers a comparable discharge capacity of 90 and 78 mAh g−1, respectively (at 0.1 A g−1), validating the advantage of the binder‐free VP/fCNT‐F electrode for AZMBs. [ABSTRACT FROM AUTHOR]

This work introduces a novel concept of electrode‖electrolyte interface enhancement using an ultraviolet (UV) light-assisted in situ polymerization strategy to improve the performance of quasi-solid-state zinc–air batteries (ZABs). The suitability of the UV polymerization strategy to process a mechanically stable OH− conducting anion exchange polymer electrolyte membrane (AEPEM) reinforced by a glass fiber (GF) separator is also reported. The in situ polymerized ionomer-skin/interlayer (a thin anion-conducting polymer coating over the air-cathode of ZAB) acts as a buffer layer to narrow down the performance gap generally observed between ZABs possessing quasi-solid-state electrolytes and standard liquid electrolytes, respectively. For instance, when combined with the in situ polymerization strategy, a rechargeable ZAB (rZAB) based on an AEPEM-GF composite membrane delivered a high power density of 140 mW cm−2, higher than that of the one without an in situ polymerized ionomer interlayer (120 mW cm−2). Notably, in a flexible rZAB configuration, this new strategy resulted in enhanced rate capability and cycling stability for 14 h at an operating current density of 2 mA cm−2. [ABSTRACT FROM AUTHOR]

Hydrogen‐bonded organic frameworks (HOFs) are ordered supramolecular solid structures, however, nothing much explored as centimetre‐scale self‐standing films. The fabrication of such crystals comprising self‐supported films is challenging due to the limited flexibility and interaction of the crystals, and therefore studies on two‐dimensional macrostructures of HOFs are limited to external supports. Herein, we introduce a novel chemical gradient strategy to fabricate a crystal‐deposited HOF film on an in situ‐formed covalent organic polymer film (Tam‐Bdca‐CGHOF). The fabricated film showed versatility in chemical bonding along its thickness from covalent to hydrogen‐bonded network. The kinetic‐controlled Tam‐Bdca‐CGHOF showed enhanced proton conductivity (8.3×10−5 S cm−1) compared to its rapid kinetic analogue, Tam‐Bdca‐COP (2.1×10−5 S cm−1), which signifies the advantage of bonding‐engineering in the same system. [ABSTRACT FROM AUTHOR]

Polymer composite electrolytes (PCEs), i.e., materials combining the disciplines of polymer chemistry, inorganic chemistry, and electrochemistry, have received tremendous attention within academia and industry for lithium‐based battery applications. While PCEs often comprise 3D micro‐ or nanoparticles, this review thoroughly summarizes the prospects of 2D layered inorganic, organic, and hybrid nanomaterials as active (ion conductive) or passive (nonion conductive) fillers in PCEs. The synthetic inorganic nanofillers covered here include graphene oxide, boron nitride, transition metal chalcogenides, phosphorene, and MXenes. Furthermore, the use of naturally occurring 2D layered clay minerals, such as layered double hydroxides and silicates, in PCEs is also thoroughly detailed considering their impact on battery cell performance. Despite the dominance of 2D layered inorganic materials, their organic and hybrid counterparts, such as 2D covalent organic frameworks and 2D metal–organic frameworks are also identified as tuneable nanofillers for use in PCE. Hence, this review gives an overview of the plethora of options available for the selective development of both the 2D layered nanofillers and resulting PCEs, which can revolutionize the field of polymer‐based solid‐state electrolytes and their implementation in lithium and post‐lithium batteries. [ABSTRACT FROM AUTHOR]

A novel class of copper-based 2D-c-MOF was synthesized from 1,3,5-triformylphloroglucinol using green mechano-chemistry. Herein, metal coordination with the salicylaldehyde functional moiety was explored for the first time in MOFs. Moreover, an intrinsic semiconductive copper-based SA-MOF thin film was fabricated using an in situ salt-free method at room temperature. [ABSTRACT FROM AUTHOR]

Expression of concern for 'Selective isolation and eradication of E. coli associated with urinary tract infections using anti-fimbrial modified magnetic reduced graphene oxide nanoheaters' by Fatima Halouane et al., J. Mater. Chem. B, 2017, 5, 8133–8142, https://doi.org/10.1039/C7TB01890H. [ABSTRACT FROM AUTHOR]

Commercially available platinum‐supported carbon (Pt/C) catalysts are the most widely used oxygen reduction reaction (ORR) electrocatalysts in polymer electrolyte membrane fuel cells (PEMFCs). However, inadequate active triple‐phase boundary formation and carbon oxidation in Pt/C during PEMFC operation shorten its lifetime and efficiency. In this direction, a new class of carbon‐free electrocatalysts for ORR is prepared by dispersing Pt nanoparticles on ZrP (Zirconium phosphates) nanoplates. In one case (ZrP@Pt), the Pt nanoparticles are found to be closely distributed and completely covering the ZrP nanoplates, whereas in the second case (Pt/ZrP), the Pt nanoparticles selectively restrict dispersion along the edges of the support. ZrP as the support displays an intrinsic proton conductivity of ≈0.5 × 10−4 S cm−1 at 70 °C, with an activation energy (Ea) of 0.19 eV. Pt/ZrP shows better durability after 3000 start‐stop cycles. The mass activity of Pt/ZrP is increased by 4.6 times compared to Pt/C, which exhibits a loss in mass activity by 1.37 times. The single‐cell level validation of ZrP@Pt, Pt/ZrP, and Pt/C as the electrocatalysts in PEMFC at an operating potential of 0.60 V shows the achievable current densities of 0.600, 0.890, and 0.890 A cm−2. [ABSTRACT FROM AUTHOR]

The development of highly active, cost‐effective, and durable, noble metal‐free oxygen reduction electrocatalysts is inevitable for the full‐fledged implementation of fuel cells and zinc–air batteries. This work reports the synthesis of heteroatom (N, P, S)‐doped metal‐free mesoporous carbon‐based electrocatalyst derived from polypyrrole by combining the ice templating, freeze‐drying, and carbonization processes. The correlation between the structure and electrochemical activity of the polypyrrole‐derived carbon‐based electrocatalyst in the presence and absence of ice templating is investigated. The optimized electrocatalyst, aided by the ice‐templating and freeze‐drying step, shows an onset and half‐wave potential (E1/2) of 0.94 and 0.78 V vs reversible hydrogen electrode, respectively, in an alkaline electrolyte (0.1 m KOH). Later, the application of the optimized electrocatalyst is demonstrated in a primary zinc–air battery (ZAB) cell. The results prove that the ZAB device performance based on the homemade catalyst is on par with that of the state‐of‐the‐art Pt/C cathode. The catalyst performance is correlated with the heteroatom doping and the enhanced porosity of the sample benefitted from ice templating. Ultimately, this work depicts a facile and rational synthesis of a truly metal‐free electrocatalyst for the primary ZABs that can be a potential replacement for state‐of‐the‐art systems. [ABSTRACT FROM AUTHOR]

The sustainable energy technology is in great demand due to the depletion and the risks associated with the use of fossil fuels. Various energy technologies like regenerative fuel cells, zinc–air batteries, and overall water-splitting devices have a huge scope in the growth of green energy. The efficiency of these devices is reliant upon the multifunctional electrocatalysts, which include both bifunctional and trifunctional electrocatalysts. Among the different categories of the materials used for such multifunctional electrocatalysis, metal–organic-frameworks (MOFs) occupy a very consolidated place because of their high surface area, porosity, and many other unique physicochemical properties. However, the use of MOFs for the trifunctional electrocatalytic applications is in the budding phase and needs to be explored more. Further, most of these MOF-based trifunctional electrocatalysts are derived by pyrolyzing MOFs at high temperatures. Therefore, there is a need to develop more conductive MOFs which can be directly utilized for the trifunctional applications. In this frontier article, we present the latest reports on the MOF-based materials for trifunctional applications. The material design strategies of the MOF-based materials for trifunctional electrocatalysis have been discussed. The progressive improvements made with MOFs in electrocatalytic applications have been provided with emphasis on the structural, active site and compositional requirements. Finally, the challenges and viewpoints on the future development of the MOF-based materials for trifunctional electrocatalysis have been provided. [ABSTRACT FROM AUTHOR]