Two-dimensional CoFe hydroxides nanostructure as positive material for asymmetric supercapacitor

Poly(azure C)-coated CoFe Prussian blue analogue nanocubes for high-energy asymmetric supercapacitors

Prussian blue analogues are considered as promising supercapacitor electrode materials due to their high theoretical capacitance and low cost. Yet, they suffer from poor electronic conductivity and cycling life. Here, a redox dye polymer, poly(azure C) (PAC), is in-situ grown uniformly on CoFe Prussian blue analogue (CoFePBA). As a polymer mediator, the PAC coating on each PBA not only enhances the electronic conductivity and surface area, but also improves the structural stability and specific capacitance of PBA. As a result, the optimized CoFePBA@PAC possesses ultrahigh specific capacitance (968.67 F g^-1 at 1 A g^-1), superior rate performance (665.78 F g^-1 at 10 A g^-1), and excellent long-cycling stability (92.45% capacity retention after 2000 cycles). As an application, a fabricated CoFePBA@PAC//AC asymmetric supercapacitor (AC = activated carbon) maintains 84.7% capacitance retention in 2000 cycles at 1 A g^-1 and displays a superior specific energy of 29.16 W h kg^-1 at the power density of 799.78 W kg^-1. These results demonstrate that redox dye polymer-coated PBAs with outstanding performance have a promising prospect in the field of energy storage.

Bifunctional nickel foam composite cathode co-modified with CoFe@NC and CNTs for electrocatalytic degradation of atrazine over wide pH range

Bifunctional cathodes have attracted widespread interest in the heterogeneous electro-Fenton (hetero-EF) process. In this study, the bifunctional composite cathode co-modified with N-doped carbon CoFe alloy (CoFe@NC) and carbon nanotubes (CNTs), designated as CoFe@NC-CNTs/CNTs/NF, integrating hydrogen peroxide (H₂O₂) synthesis and catalysis, was prepared for efficient degradation of atrazine (ATZ) under the near-neutral condition (pH_i = 5.9). The morphology properties, crystal structure, microstructures, and elemental composition were determined. The influences of current density, initial pH value, different anions, and water matrix on the removal of ATZ were systematically studied. In the hetero-EF process, high removal efficiencies of ATZ can be achieved over the broad pH range (3-9) under the current density of 4.5 mA cm^-2. The removal efficiency of ATZ remained at 90.2 ± 0.3% after 8 cycles under the near-neutral condition (pH_i = 5.9). Radical quenching tests and EPR spectra have verified that both free radical pathways such as superoxide anion (O₂·^-) and hydroxyl radical (·OH) and non-radical pathway such as singlet oxygen (¹O₂) contributed to ATZ removal. The degradation pathways and catalytic mechanism were proposed. Toxicity evaluation and Escherichia coli growth test showed that the toxicity gradually decreased during the degradation process. This work provided a new thought for developing an efficient and stable bifunctional cathode to construct an in-situ hetero-EF system for pollutants removal over the wide pH range.