Rechargeable aqueous Zn-ion energy storage devices are promising candidates for next-generation energy storage technologies. However, the lack of highly reversible Zn2+-storage anode materials with low potential windows remains a primary concern. Here, we report a two-dimensional polyarylimide covalent organic framework (PI-COF) anode with high-kinetics Zn2+-storage capability. The well-organized pore channels of PI-COF allow the high accessibility of the build-in redox-active carbonyl groups and efficient ion diffusion with a low energy barrier. The constructed PI-COF anode exhibits a specific capacity (332 C g–1 or 92 mAh g–1 at 0.7 A g–1), a high rate capability (79.8% at 7 A g–1), and a long cycle life (85% over 4000 cycles). In situ Raman investigation and first-principle calculations clarify the two-step Zn2+-storage mechanism, in which imide carbonyl groups reversibly form negatively charged enolates. Dendrite-free full Zn-ion devices are fabricated by coupling PI-COF anodes with MnO2 cathodes, delivering excellent energy densities (23.9 ∼ 66.5 Wh kg–1) and supercapacitor-level power densities (133 ∼ 4782 W kg–1). This study demonstrates the feasibility of covalent organic framework as Zn2+-storage anodes and shows a promising prospect for constructing reliable aqueous energy storage devices.

Three unprecedented helical nanographenes (1, 2, and 3) containing an azulene unit are synthesized. The resultant helical structures are unambiguously confirmed by X‐ray crystallographic analysis. The embedded azulene unit in 2 possesses a record‐high twisting degree (16.1°) as a result of the contiguous steric repulsion at the helical inner rim. Structural analysis in combination with theoretical calculations reveals that these helical nanographenes manifest a global aromatic structure, while the inner azulene unit exhibits weak antiaromatic character. Furthermore, UV/Vis‐spectral measurements reveal that superhelicenes 2 and 3 possess narrow energy gaps (2: 1.88 eV; 3: 2.03 eV), as corroborated by cyclic voltammetry and supported by density functional theory (DFT) calculations. The stable oxidized and reduced states of 2 and 3 are characterized by in‐situ EPR/Vis–NIR spectroelectrochemistry. Our study provides a novel synthetic strategy for helical nanographenes containing azulene units as well as their associated structures and physical properties.

The structure of emeraldine salt and emeraldine bases with different molar weight and their behavior in electrochemical doping was studied by different spectroscopic and spectroelectrochemical techniques. By Fourier transform infrared (FTIR) spectroscopy, the branching of the polymer chain at tri- and tetrasubstituted benzene rings as well as the presence of small amounts of phenazine units are shown. The branching of the polymer chains increases with the increasing of the molar weight of emeraldines. The optical transitions in protonated and unprotonated emeraldine were studied by ultraviolet-visible near-infrared (UV-vis NIR) spectroscopy. By comparison of the electron spin resonance (ESR) spectra of emeraldine in protic solvents and acidic solutions, the emeraldine bases are shown to be to some extent protonated. Applying in situ ESR-UV-vis NIR spectroelectrochemistry, the charged states in emeraldines upon p-doping were investigated considering the influence of the nonideal "linear" polymer structures. The initial stage of oxidation of the emeraldine base and salt consists of the different charged states. The phenazine units in the polymer chains stabilize the charged states in the emeraldines upon p-doping.

Rechargeable aluminium (Al) batteries (RABs) have long‐been pursued due to the high sustainability and three‐electron‐transfer properties of Al metal. However, limited redox chemistry is available for rechargeable Al batteries, which restricts the exploration of cathode materials. Herein, we demonstrate an efficient Al–amine battery based on a quaternization reaction, in which nitrogen (radical) cations (R3N.+ or R4N+) are formed to store the anionic Al complex. The reactive aromatic amine molecules further oligomerize during cycling, inhibiting amine dissolution into the electrolyte. Consequently, the constructed Al–amine battery exhibits a high reversible capacity of 135 mAh g−1 along with a superior cycling life (4000 cycles), fast charge capability and a high energy efficiency of 94.2 %. Moreover, the Al–amine battery shows excellent stability against self‐discharge, far beyond conventional Al–graphite batteries. Our findings pave an avenue to advance the chemistry of RABs and thus battery performance.

The disinfection of bacteria by thermally excited pyroelectric materials in aqueous environments provides opportunities for the development of new means of sanitization. However, little is known about the formation of reactive oxygen species (ROS) at the surface of the thermally excited pyroelectric materials. To investigate the pyroelectrically driven ROS generation we performed OH radical specific measurements of thermally stimulated barium titanate nanoparticles in contact with palladium nanoparticles. Through electron spin resonance measurements with the spin trap BMPO (5-tert-butoxycarbonyl 5-methyl-1-pyrroline n-oxide) and fluorescence spectroscopy of 7-hydroxycoumarin, OH radical generation was detected, which confirms the hypothesis of pyroelectric ROS production. Since pyroelectric potential changes are insufficient for direct electrochemical OH radical generation, we propose a two-step chargetransfer model facilitated by intermittent contact between the palladium and the pyroelectric nanoparticles and the pyroelectric effect as the driving force for charge transfer. ■ INTRODUCTIONCommercial water disinfection currently relies on chemical methods using chlorine-or ozone-based chemicals, whereas physical methods like thermal disinfection or ultraviolet radiation are less often employed. Due to their high oxidative potential, reactive oxygen species (ROS) are well suited as a physical means of disinfection. A completely new approach for creating ROS is the utilization of the pyroelectric effect, 1 which seems favorable when naturally occurring temperature changes can be employed for the excitation of the pyroelectric materials and, thus, offer an environmentally friendly method of water disinfection.In an aqueous solution the spontaneous polarization at the surface of a ferroelectric is screened, for example, by dissolved ions or dissociated water molecules. Changes in temperature trigger the pyroelectric effect. The imbalance of polarization and screening charges changes the effective surface potential. It was shown that these potential changes whether they stem from changes in temperature or strain can be used to drive electrochemistry between physisorbed molecular species. 1,2 For example Hong et al. demonstrated water splitting on mechanically excited surfaces of BaTiO 3 and ZnO. Gutmann et al. proposed that the observed water disinfection with thermally stimulated LiNbO 3 and LiTaO 3 is facilitated by production of ROS at the surface of the pyroelectric materials.Free radicals have high oxidation potentials, especially the OH radical whose oxidation potential is twice that of chlorine which is commonly used for disinfection. It is known that OH radicals can pull H atoms from C−H and S−H bonds and split aromatic rings. Living cells are damaged by radicals reacting with amino acids and DNA molecules. 3 Photocatalytic E. coli inactivation with TiO 2 showed cell damage caused by various ROS, such as OH radicals, hyperoxide radicals, and H 2 O 2 . 4 Basically ROS react immediately at the place of their ori...

The electrochemical doping of emeraldine salt and emeraldine bases with different weight average molecular weights was studied by in situ Fourier transform infrared (FTIR) spectroelectrochemistry using attenuated total reflection (ATR) technique. The formation and stabilization of charge carriers in polyaniline during p-doping was followed in dependence of the chain branching. The potential dependence of the IR bands during the oxidation of the polymer clearly demonstrates the formation of the different charged polymer structures (π-dimers, polarons, and bipolarons). It is shown that IR bands usually attributed to a semiquinoid polaron lattice correspond in fact to doubly charged species, π-dimers, which are face-to-face complexes of two polarons. Bands corresponding exclusively to polarons have been identified at 1266, 1033, and 1010 cm(-1), suggesting that polarons are predominantly stabilized on the linear segments near the polymer branches by phenazine.

The role of the phenazine structure in the stabilization of charged states in polyaniline was studied by in situ electron spin resonance (ESR)-UV/vis-near-infrared (NIR) spectroelectrochemistry of polyaniline and the copolymers of aniline and a phenazine derivative (3,7-diamino-5-phenylphenazinium chloride, phenosafranine). It is shown that the copolymer can be prepared by electropolymerization, and its structure was confirmed by mass spectrometry and IR spectroscopy. The electrochemistry of polyaniline and its copolymer pointed to preferred stabilization of a polaron pair in the charged states at the initial charge transfer reaction instead of polarons that are formed by equilibrium reaction at higher electrode potentials. A second polaron pair is detected for higher doped states of the polymer films. A mechanism of the formation of charged states in polyaniline and their equilibrium is given. It is shown that in situ ESR-UV/vis-NIR spectroelectrochemistry is the method of choice to differentiate between polarons and polaron pairs in their potential-dependent formation. Thus, by this in situ spectroelectrochemical method the influence of phenazine structure on the formation of polarons in aniline polymers and copolymers can be followed.

The structure and stabilization of charged states during p-doping of polyaniline (PANI) were studied by in situ ATR-FTIR spectroelectrochemistry. The role of phenazine-like units in several copolymers of aniline and a phenazine derivative (3,7-diamino-5-phenylphenazinium chloride, phenosafranine) was investigated by spectroelectrochemistry. PANI and three copolymers with different aniline to phenosafranine ratio were electrochemically prepared. FTIR spectra of as-prepared polymers as well as in situ FTIR spectra during the oxidation of the polymers give evidence of the presence of phenazine-like units in the structure of electrochemically prepared PANI, as shown by vibrations of the phenazine rings. New bands corresponding to the in-plane and out-of-plane C-H vibration of 1,2,4-trisubstituted benzene nuclei in the phenazine skeleton are found at 1033, 957, 880, 766 and 681 cm(-1). The potential dependence of IR bands observed during oxidation of the polymers was compared to that of the ESR intensity and the absorption data and points to the diamagnetic species like π-dimers formed at higher oxidation level of PANI. This charged state is shown to be fixed at the link of the phenazine-like units with the linear segments of PANI.