Tetra-β-nitro-substituted phthalocyanines: a new organic electrode material for lithium batteries

Single-Point Linkage Engineering in Conjugated Phthalocyanine-Based Covalent Organic Frameworks for Electrochemical CO2 Reduction

The utilization of covalent organic frameworks (COFs) holds great potential for achieving tailorable tuning of catalytic performance through bottom-up modulation of the reticular structure. In this work, we show that a single-point structural alteration in the linkage within a nickel phthalocyanine (NiPc)-based series effectively modulates the catalytic performance of the COFs in electrochemical CO2 reduction reaction (CO2RR). A NiPc-based COF series with three members which possess the same NiPc unit but different linkages, including piperazine, dioxin, and dithiine, have been constructed by nucleophilic aromatic substitution reaction between octafluorophthalocyanine nickel and tetrasubstituted benzene linkers with different bridging groups. Among these COFs, the dioxin-linked COF showed the best activity of CO2RR with a current density of CO (jCO) =  - 27.99 mA cm-2 at - 1.0 V (versus reversible hydrogen electrode, RHE), while the COF with piperazine linkage demonstrated an excellent selectivity of Faradaic efficiency for CO (FECO) up to 90.7% at a pretty low overpotential of 0.39 V. In addition, both a high FECO value close to 100% and a reasonable jCO of - 8.20 mA cm-2 at the potential of - 0.8 V (versus RHE) were obtained by the piperazine-linked COF, making it one of the most competitive candidates among COF-based materials. Mechanistic studies exhibited that single-point structural alteration could tailor the electron density in Ni sites and alter the interaction between the active sites and the key intermediates adsorbed and desorbed, thereby tuning the electrochemical performance during CO2RR process.

Design and Regulation of Anthraquinone's Electrochemical Properties in Aqueous Zinc-Ion Batteries via Benzothiadiazole and Its Dinitro Derivatives

Organic cathode materials are widely considered as highly promising for aqueous zinc-ion batteries (AZIBs) due to their tunable properties, low cost, and ease of processing and synthesis. Benzothiadiazoles have demonstrated significant potential as organic electrode materials in AZIBs, owing to their strong electron-accepting capabilities and the presence of multiple reversible redox sites in anthraquinone. In this study, we designed a polymer, poly(2-methyl-6-(7-methyl-5,6-dinitrobenzo[c][1,2,5]thiadiazol-4-yl)anthracene-9,10-dione) (PBDQ), with multielectron transfer capability through a copolymerization approach. Additionally, we synthesized another polymer, poly2,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)anthracene-9,10-dione(PBDQ-N), by introducing two electron-withdrawing nitro groups on the aromatic ring of benzothiadiazole. The introduction of nitro groups, with their unique electronic properties, enhances electron delocalization and increases the number of electrochemically active sites, thereby promoting faster zinc-ion insertion/extraction reactions. Experimental results show that both PBDQ and PBDQ-N exhibit excellent electrochemical properties due to the abundance of active sites and extended π-conjugation. Among them, PBDQ-N demonstrates outstanding performance, including an ultrahigh specific capacity of 446.2 mAh g-1 at 0.1 A g-1 and excellent cycle life exceeding 20,000 cycles at 10 A g-1. Moreover, the lower lowest-unoccupied molecular orbital (LUMO) energy level and improved conductivity of PBDQ-N provide a fast electron transfer rate, resulting in a higher Zn2+ diffusion coefficient (3.47 × 10-11-2.6 × 10-8 cm2 s-1) and exceptional rate performance (234.6 mAh g-1 at 10 A g-1). Theoretical calculations and ex situ characterizations confirm that C═O, C═N, and N═O groups all participate as active sites in Zn2+ storage. This work highlights how molecular design and the introduction of functional groups, such as nitro groups, can effectively regulate the electrochemical properties of organic polymers in AZIBs. It also demonstrates the impact of these strategies on the electrochemical performances of these materials when they are used as cathodes in aqueous zinc-ion batteries.

1,4,5,8-Naphthalenetetracarboxylic dianhydride grafted phthalocyanine macromolecules as an anode material for lithium ion batteries

For solving the problems of high solubility in electrolytes, poor conductivity and low active site utilization of organic electrode materials, in this work, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) grafted nickel phthalocyanine (TNTCDA-NiPc) was synthesized and used as an anode material for lithium ion batteries. As a result, the dispersibility, conductivity and dissolution stability are improved, which is conducive to enhancing the performance of batteries. The initial discharge capacity of the TNTCDA-NiPc electrode is 859.8 mA h g^-1 at 2 A g^-1 current density, which is much higher than that of the NTCDA electrode (247.4 mA h g^-1). After 379 cycles, the discharge capacity of the TNTCDA-NiPc electrode is 1162.9 mA h g^-1, and the capacity retention rate is 135.3%, which is 7 times that of the NTCDA electrode. After NTCDA is grafted to the phthalocyanine macrocyclic system, the dissolution of the NTCDA in the electrolyte is reduced, and the conductivity and dispersion of the NTCDA and phthalocyanine ring are also improved, so that more active sites of super lithium intercalation from NTCDA and phthalocyanine rings are exposed, which results in better electrochemical performance. The strategy of grafting small molecular active compounds into macrocyclic conjugated systems used in this work can provide new ideas for the development of high performance organic electrode materials.

Porous diatomite-mixed 1,4,5,8-NTCDA nanowires as high-performance electrode materials for lithium-ion batteries

A porous composite electrode composed of diatomite-mixed 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) is prepared by electrostatic spinning technology. Compared with traditional coated electrodes without diatomite mixing, the obtained composite electrode materials have higher porosity, larger specific surface area and faster lithium ion transport channels, which makes them exhibit better electrochemical performance, such as smaller impedance, higher capacity, and better cycling stability and rate performance. The electrospun diatomite-mixed 1,4,5,8-NTCDA composite (ED-1,4,5,8-NTCDA) electrode shows an initial coulombic efficiency of 77.2%, which is much higher than that of the electrospun 1,4,5,8-NTCA (E-1,4,5,8-NTCDA) electrode without diatomite mixing (63.8%) and the coated 1,4,5,8-NTCA (C-1,4,5,8-NTCDA) electrode (48.3%). Moreover, the ED-1,4,5,8-NTCDA electrode displays an initial discharge capacity of 1106.5 mA h g-1, which is much higher than that of the E-1,4,5,8-NTCDA electrode (546.0 mA h g-1) and the C-1,4,5,8-NTCDA electrode (185.4 mA h g-1). After 200 cycles, the capacity of the ED-1,4,5,8-NTCDA electrode remains at 1008.5 mA h g-1 with a retention ratio of 91.2%, which is also much higher than that of 753.2 mA h g-1 for the E-1,4,5,8-NTCDA electrode and 288.1 mA h g-1 for the C-1,4,5,8-NTCDA electrode. Even at a higher current density of 1500 mA g-1, its capacity remains above 508.9 mA h g-1. The ED-1,4,5,8-NTCDA electrode presents superior performance, which opens up a promising new approach for further utilization of organic materials as electrode materials in rechargeable lithium-ion batteries.

Atypical Film-Forming Behavior of Soluble Tetra-3-Nitro-Substituted Copper Phthalocyanine

Thin films of metal phthalocyanines (MPc) are known to exhibit excellent physical properties but poorly controlled morphologies. Therefore, the present work seeks to understand the film growth mechanism of a model compound for potentially usable MPc, specifically, copper tetra(3-nitro-5-tert-butyl)phthalocyanine (CuPc*). The Langmuir-Schaefer (LS) technique was applied to prepare a series of CuPc* films under different processing conditions. The film growth was examined by Brewster angle microscopy (BAM) on the water surface and small-angle X-ray scattering (SAXS) from the solid films. Neutron reflectometry (NR) measurements of the water uptake into the films and computer simulation of hydrated CuPc* were performed to substantiate an idea of colloidal MPc-water aggregates as nanoscale precursors of smooth solid films. This idea appears fruitful in terms of materials chemistry.