Hierarchical Hybrids Integrated by Dual Polypyrrole-Based Porous Carbons for Enhanced Capacitive Performance

The impact of physicochemical features of carbon electrodes on the capacitive performance of supercapacitors: a machine learning approach

Hybrid electric vehicles and portable electronic systems use supercapacitors for energy storage owing to their fast charging/discharging rates, long life cycle, and low maintenance. Specific capacitance is regarded as one of the most important performance-related characteristics of a supercapacitor's electrode. In the current study, Machine Learning (ML) algorithms were used to determine the impact of various physicochemical properties of carbon-based materials on the capacitive performance of electric double-layer capacitors. Published experimental datasets from 147 references (4899 data entries) were extracted and then used to train and test the ML models, to determine the relative importance of electrode material features on specific capacitance. These features include current density, pore volume, pore size, presence of defects, potential window, specific surface area, oxygen, and nitrogen content of the carbon-based electrode material. Additionally, categorical variables as the testing method, electrolyte, and carbon structure of the electrodes are considered as well. Among five applied regression models, an extreme gradient boosting model was found to best correlate those features with the capacitive performance, highlighting that the specific surface area, the presence of nitrogen doping, and the potential window are the most significant descriptors for the specific capacitance. These findings are summarized in a modular and open-source application for estimating the capacitance of supercapacitors given, as only inputs, the features of their carbon-based electrodes, the electrolyte and testing method. In perspective, this work introduces a new wide dataset of carbon electrodes for supercapacitors extracted from the experimental literature, also giving an instance of how electrochemical technology can benefit from ML models.

Enhancing Electrochemical Biosensor Performance for 17β-Estradiol Determination with Short Split-Aptamers

Chronic exposure of 17β-estradiol (E2) even at low concentration can disorganize the endocrine system and lead to undesirable health problems in the long run. An electrochemical biosensor for rapid detection of E2 in water samples was successfully developed. The biosensor was based on split DNA aptamers attached onto poly (methacrylic acid-co-n butyl acrylate-succinimide) microspheres deposited on polypyrrole nanowires coated electrode (PPY/PMAA-NBA). The sandwich paired of split DNA aptamers used were truncated from 75 mer parent aptamers. These two strands of 12-mer and 14-mer split DNA aptamers were then immobilized on the PMAA-NBA microspheres. In the presence of E2, the split DNA aptamers formed an apt12-E2-apt14 complex, where the binding reaction on the electrode surface led to the detection of E2 by differential pulse voltammetry using ferrocyanide as a redox indicator. Under optimum conditions, the aptasensor detected E2 concentrations in the range of 1 × 10-4 M to 1 × 10-12 M (R2 = 0.9772) with a detection limit of 4.8 × 10-13 M. E2, which were successfully measured in a real sample with 97-104% recovery and showed a good correlation (R2 = 0.9999) with the established method, such as high-performance liquid chromatography. Interactions between short and sandwich-type aptamers (split aptamers) demonstrated improvement in aptasensor performance, especially the selectivity towards several potential interferents.

Nanoporous carbon materials as a sustainable alternative for the remediation of toxic impurities and environmental contaminants: A review

Due to rapidly deteriorating water resources, the world is looking forward to a sustainable alternative for the remediation of noxious pollutants such as heavy metals and organic and gaseous contaminants. To address this global issue of environmental pollution, nanoporous carbon materials (NPCMs) can be used as a one-stop solution. They are widely applied as adsorbents for many toxic impurities and environmental contaminants. The present review provides a detailed overview of the role of different synthesis factors on the porous characteristics of carbon materials, activating agents, reagent-precursor ratio and their potential application in the remediation. Findings revealed that synthetic parameters result in the formation of microporous NPCMs (S_BET: >4000 m³/g; V_Total (cm³/g) ≥ 2; V_Micro (cm³/g) ≥ 1), micromesoporous (S_BET: >2500 m³/g; V_Total (cm³/g) ≥ 1.5; V_Micro (cm³/g) ≥ 0.7) and mesoporous (S_BET: >2500 m³/g; V_Total (cm³/g) ≥ 1.5; V_Micro (cm³/g) ≥ 0.5) NPCMs. Moreover, it was observed that a narrow pore size distribution (0.5-2.0 nm) yields excellent results in the remediation of noxious contaminants. Further, chemical activating agents such as NaOH, KOH, ZnCl₂, and H₃PO₄ were compared. It was observed that activating agents KОН, H₃PO₄, and ZnCl₂ were generally used and played a significant role in the possible large-scale production and commercialization of NPCMs. Thus, it can be interpreted that with a well-planned strategy for the synthesis, NPCMs with a "tuned" porosity for a specific application, in particular, microporosity for the accumulation and adsorption of energetically important gases (CO₂, CH₄, H₂), micro-mesoporosity and mesoporosity for high adsorption capacity for towards metal ions and a large number of dyes, respectively.

Facile synthesis of tetraphenylethene-based conjugated microporous polymers as adsorbents for CO2 and organic vapor uptake

We present three novel conjugated microporous polymers (CMP@1–3), which were formed by an imidization reaction between tetra-(4-aminophenyl)ethylene and anhydrides.

Preparation of reduced graphene oxide nanosheet/FexOy/nitrogen-doped carbon layer aerogel as photo-Fenton catalyst with enhanced degradation activity and reusability

In this manuscript, a novel reduced graphene oxide nanosheet/Fe_xO_y/nitrogen-doped carbon layer (rGS/Fe_xO_y/NCL) aerogel with Fe_xO_y NPs sandwiched between rGS and NCL was prepared via a two-step method. Their catalytic performance was evaluated in a photo-Fenton degradation of rhodamine B. It was found that rGS/Fe_xO_y/NCL aerogel represented higher degradation activity than the sum of rGS/NCL support and Fe_xO_y NPs, suggesting synergistic effect was established between support and reactive species. The degradation activity was investigated on the basis of aerogel usage, Fe_xO_y loading, H₂O₂ dosage, pH value and RhB concentration. To test stability and reusability, leaching experiments, cyclic experiments and structural analysis were carried out. Based on inhibitor experiment and intermediate detection, a possible catalytic mechanism and degradation pathway of RhB were proposed.

A solid-state chemical method for synthesizing MgO nanoparticles with superior adsorption properties

As a traditional and effective adsorbent, MgO is a low-cost, eco-friendly, nontoxic, and economical material for wastewater treatment. However, multistep processing and the use of organic agents result in high costs and lead to environmental pollution, strongly inhibiting the practical application of MgO. Herein, a simple solid-state chemical route has been used to prepare small-sized MgO nanoparticles with a large specific surface area of 213 m2 g-1 without using liquid solvents, template agents, or surfactants. This facile method is a green strategy that is suitable for large-scale production, avoiding complex preparation processes and serious environmental pollution. The obtained small-sized MgO nanoparticles showed a superior adsorption capacity of 2375 mg g-1 towards Congo red, originating from the large specific surface area and surface features (hydrogen bonds and electrostatic interactions). The adsorption behavior obeyed a pseudo-second-order rate equation and the Langmuir isotherm adsorption model. This study provides a route for the synthesis of oxides with large specific surface areas and obtained an adsorbent with superior adsorption capacity.

CO2-Assisted synthesis of hierarchically porous carbon as a supercapacitor electrode and dye adsorbent

A facile and sustainable strategy was developed for the fabrication of hierarchically porous carbons with tunable pore size distributions and architectures.

Fabrication of nitrogen-rich three-dimensional porous carbon composites with nanosheets and hollow spheres for efficient supercapacitors

N-Rich 3D porous carbon composites with nanosheets and hollow spheres have been fabricated for efficient supercapacitors.

Hydrophilic “bridge” tannins for stabilizing the metal selenides onto activated carbon for binder-free and ultralong-life asymmetric supercapacitors

Tannin-doped activated carbon by employing tannin as the structure coupling bridge between the two components could effectively tune the electronic structural states and result in strong coupling effects with NiCo₂Se₄.

Facile synthesis of bio-based nitrogen- and oxygen-doped porous carbon derived from cotton for supercapacitors

Biomass-derived O- and N-doped porous carbon has become one of the most competitive supercapacitor electrode material because of its renewability and sustainability.