Electrocatalytic and supercapacitor performance of Phosphorous and Nitrogen co-doped Porous Carbons synthesized from Aminated Tannins

Comprehensive Analysis of Hierarchical Porous Carbons Using a Dual-Shape 2D-NLDFT Model with an Adjustable Slit-Cylinder Pore Shape Boundary

A thorough characterization of the textural properties of hierarchical porous carbons (HPCs) is of utmost importance as it provides information that aids in the selection of a suitable material for a given application and in understanding the phenomena observed once the material becomes part of a system. Gas adsorption-desorption isotherms coupled with the application of density functional theory (DFT) models to these isotherms are common tools for the textural characterization of HPCs, for which pore shape is an essential factor for the determination of pore size distributions (PSDs). By analyzing the experimental adsorption data of a series of CO₂-activated HPCs with a progressive development of porosity, it is shown that artifacts are found in the derived PSDs when a slit-cylinder pore shape boundary is fixed at 2 nm, which is the case for the original dual-shape nonlocal DFT (2D-NLDFT-HS) and hybrid quenched solid DFT (QSDFT) models. This study presents a new dual-shape 2D-NLDFT-HS (DS-HS) model that, combined with the 2D-NLDFT-HS model for CO₂, provides the possibility of analyzing simultaneously N₂ and CO₂ adsorption-desorption isotherms and adjusting at the same time the limits for the assumed slit and cylindrical pore shapes. Using the DS-HS approach and adjusting the slit-cylinder boundary at 3 nm allowed eliminating PSDs artifacts. The interactive adjustment of the slit-cylindrical pore shape boundary of the DS-HS model represents a major advantage of this approach allowing for a comprehensive analysis of the adsorption data and a more accurate description of the textural properties of HPC materials.

Metal-Free Carbon-Based Supercapacitors—A Comprehensive Review

Herein, metal-free heteroatom doped carbon-based materials are being reviewed for supercapacitor and energy applications. Most of these low-cost materials considered are also derived from renewable resources. Various forms of carbon that have been employed for supercapacitor applications are described in detail, and advantages as well as disadvantages of each form are presented. Different methodologies that are being used to develop these materials are also discussed. To increase the specific capacitance, carbon-based materials are often doped with different elements. The role of doping elements on the performance of supercapacitors has been critically reviewed. It has been demonstrated that a higher content of doping elements significantly improves the supercapacitor behavior of carbon compounds. In order to attain a high percentage of elemental doping, precursors with variable ratios as well as simple modifications in the syntheses scheme have been employed. Significance of carbon-based materials doped with one and more than one heteroatom have also been presented. In addition to doping elements, other factors which play a key role in enhancing the specific capacitance values such as surface area, morphology, pore size electrolyte, and presence of functional groups on the surface of carbon-based supercapacitor materials have also been summarized.

Heterogeneous sonocatalytic degradation of an anionic dye in aqueous solution using a magnetic lanthanum dioxide carbonate-doped zinc ferrite-reduced graphene oxide nanostructure

We report herein the sonochemical synthesis of a lanthanum dioxide carbonate (La₂O₂CO₃) and zinc ferrite (ZnFe₂O₄)-loaded reduced graphene oxide (LZF-rGO) nanoheterostructure for ultrasound (US)-assisted degradation of methyl orange (MO) from water. The MO was chosen as a model organic dye due to its toxicological and biodegradable-resistant properties. The LZF-rGO catalyst was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results of characterizations confirmed successful synthesis of sonocatalyst. Among different removal systems, US/LZF-rGO displayed outstanding sonodegradation performance for degradation of MO. The maximum removal efficiency of 75.9% was achieved using 0.2 g/L sonocatalyst, 20 mg/L MO, and 0.71 W/cm² US power intensity for 65 min. MO can be partially adsorbed on LZF-rGO but mostly sonodegraded by reactive radical species. The reaction conditions were optimized by investigating the effect of key operating parameters, including the sonocatalyst dosage, initial MO concentration, US power intensity, presence of inorganic salts, and use of an enhancer, on the decolorization of MO. The degradation intermediates produced from MO during the sonocatalytic process were identified by UPLC^®/MS-MS, and possible mechanism and pathway for the degradation of MO in the US/LZF-rGO system were also proposed. Reusability experiments with this sonocatalyst revealed a less than 10% drop in the degradation efficiency after four adsorption-desorption cycles.

Synthesis of morphology-tunable electroactive biomass/graphene composites using metal ions for supercapacitors

Tannic acid (TA) is a natural polyphenolic biomass, which shows high electro-activity and can be considered for supercapacitor applications. However, the negligible electronic conductivity of TA hinders its direct use as an electrode. In order to achieve the electrochemical activity of TA, herein, a three-dimensional porous TA/graphene composite (TAG) is prepared by mixing TA with graphene oxide (GO) via hydrothermal assembly, and various structural composites are realized by adding metal ions into the system before hydrothermal treatment. Metal ions can chelate with TA molecules and coordinate with GO via electrostatic interactions. As a result, a uniform and well-defined three-dimensional porous network (TAGNi), a regularly arranged scale-like microstructure (TAGCu) and a flower-like structure (TAGFe) are achieved by introducing Ni2+, Cu2+ and Fe3+, respectively. The as-prepared TAG, TAGNi, TAGCu and TAGFe electrodes exhibit a high specific capacitance of 373.6, 412.4, 460.4 and 429.4 F g-1 at 1 A g-1, respectively, and excellent cycling stability. The TAG, TAGNi, TAGCu and TAGFe assembled symmetric supercapacitors display a favorable energy density of 14.76, 16.76, 19.13 and 17.6 W h kg-1 at 300 W kg-1, respectively. The morphology-tunable TA/graphene composites with excellent electrochemical performance are promising for renewable energy storage device applications.

A shiitake-derived nitrogen/oxygen/phosphorus co-doped carbon framework with hierarchical tri-modal porosity for high-performance electrochemical capacitors

A shiitake-derived N/O/P co-doped carbon framework with hierarchical tri-modal porosity was scalably fabricated, and exhibited exceptional supercapacitances, thanks to synergistic contributions from architectural/compositional merits.

Facile synthesis of N/P co-doped carbons with tailored hierarchically porous structures for supercapacitor applications

A facile process was designed to synthesize nitrogen/phosphorous co-doped hierarchically porous carbons with excellent performance for supercapacitors.