Carbonized Enteromorpha prolifera with porous architecture and its polyaniline composites as high-performance electrode materials for supercapacitors

Seaweed’s Role in Energetic Transition—From Environmental Pollution Challenges to Enhanced Electrochemical Devices

Simple Summary

Earth is currently facing the effects of climate change in all environmental ecosystems; this, together with pollution, is the cause of species extinction and biodiversity loss. Thus, it is vital to take actions to mitigate and decrease the release of greenhouse gases to the atmosphere. The emergence of energetic transition from fossil fuels to greener energies is clearly defined in the United Nations 2030 agenda. Although this transition endorses the ambitious goal to supply greener energy for all developed societies, the increased demand for the minerals essential to develop cleaner energetic technologies has highlighted several economic and environmental issues. Currently, these minerals are mainly obtained by mining activities that generate high levels of soil and water pollution, coupled with the intensive use of water and hazardous gas release. On the other hand, the exponential increase of electronic waste derived from end-of-life electronic equipment is already raising environmental concerns due to heavy metal contamination as a result of their disposal. Thus, it is vital to develop sustainable and efficient strategies to mitigate energetic transition environmental footprints. This review highlights the use of seaweed biomass for toxic mineral bioremediation, recycling, and as an alternative material for greener energy-storage device development.

Abstract

Resulting from the growing human population and the long dependency on fossil-based energies, the planet is facing a critical rise in global temperature, which is affecting all ecosystem networks. With a growing consciousness this issue, the EU has defined several strategies towards environment sustainability, where biodiversity restoration and preservation, pollution reduction, circular economy, and energetic transition are paramount issues. To achieve the ambitious goal of becoming climate-neutral by 2050, it is vital to mitigate the environmental footprint of the energetic transition, namely heavy metal pollution resulting from mining and processing of raw materials and from electronic waste disposal. Additionally, it is vital to find alternative materials to enhance the efficiency of energy storage devices. This review addresses the environmental challenges associated with energetic transition, with particular emphasis on the emergence of new alternative materials for the development of cleaner energy technologies and on the environmental impacts of mitigation strategies. We compile the most recent advances on natural sources, particularly seaweed, with regard to their use in metal recycling, bioremediation, and as valuable biomass to produce biochar for electrochemical applications.

Efficient microwave absorber and supercapacitors derived from puffed-rice-based biomass carbon: Effects of activating temperature

Biomass-based carbon is gaining increasing attention because it presents a promising prospect for economic growth and social sustainable development. Moreover, it is an excellent medium for application in electromagnetic and electronic devices. Here, puffed-rice-based carbon is obtained at various activating temperatures, and when the hollow bulges on the carbon disappear, the morphology of the carbon changes into sheet-like structures. The R-800 sample displays the highest I_D/I_G value and demonstrates the best performance when used as both a microwave absorber and an electrode material. The minimum reflection loss (RL) and bandwidth for RL < -10 dB of the R-800 sample reach -72.1 dB and 13.2 GHz, respectively, and the bandwidth for RL < -20 dB is as large as 7.0 GHz, illustrating the widest bandwidth among the five carbon specimens. The multiple reflection effects and scattering, good impedance matching, and interfacial polarization synergistically enhance the microwave absorption performances of the sample. At 1 A g^-1, the specific capacitance of the R-800 sample reaches 117.2 F g^-1 and the capacitance retention remains at 85.3%. Moreover, a hybrid supercapacitor R-800//R-800 demonstrates an outstanding energy density of 15.23 Wh kg^-1, power density of 5739.43 W kg^-1, and high cycle stability (94.5% after 5000 cycles). This functionalized biomass carbon provides a promising media for constructing a bridge between sustainable development and biomass materials.

Novel three-dimensional polyaniline nanothorns vertically grown on buckypaper as high-performance supercapacitor electrode

Combining polyaniline (PANI) with different dimensional carbon materials is an effective way to solve the disadvantages of poor rate performance and cycling stability induced by the structure destruction of conductive polymer materials over long-term charge/discharge cycles. In this work, novel three-dimensional (3D) conical PANI nanothorns are synthesized on a buckypaper substrate via a controlled electropolymerization process. Benefiting from the synergistic effect of the vertical growth of PANI nanothorns and the excellent mechanical elasticity of multi-wall carbon nanotubes, it can effectively alleviate the volume change during the charging and discharging process of the electrode material and ensure the rapid transmission of electrons. The morphology and structure of the composite have been characterized by scanning electron microscopy, x-ray diffraction, and Fourier transform infrared spectroscopy. The results show that the electrode exhibits a high specific capacitance of 742 F g^-1 at 1 A g^-1 in 1 M of H₂SO₄ electrolyte and a capacitance retention of 76% after 2000 cycles. The novel 3D PANI nanothorn/buckypaper composite has significant potential as practical for use as electrode materials of supercapacitors due to its easy synthesis, low cost, and high specific capacitance.

Review on Carbon/Polyaniline Hybrids: Design and Synthesis for Supercapacitor

Polyaniline has been widely used in high-performance pseudocapacitors, due to its low cost, easy synthesis, and high theoretical specific capacitance. However, the poor mechanical properties of polyaniline restrict its further development. Compared with polyaniline, functionalized carbon materials have excellent physical and chemical properties, such as porous structures, excellent specific surface area, good conductivity, and accessibility to active sites. However, it should not be neglected that the specific capacity of carbon materials is usually unsatisfactory. There is an effective strategy to combine carbon materials with polyaniline by a hybridization approach to achieve a positive synergistic effect. After that, the energy storage performance of carbon/polyaniline hybridization material has been significantly improved, making it a promising and important electrode material for supercapacitors. To date, significant progress has been made in the synthesis of various carbon/polyaniline binary composite electrode materials. In this review, the corresponding properties and applications of polyaniline and carbon hybrid materials in the energy storage field are briefly reviewed. According to the classification of different types of functionalized carbon materials, this article focuses on the recent progress in carbon/polyaniline hybrid materials, and further analyzes their corresponding properties to provide guidance for the design, synthesis, and component optimization for high-performance supercapacitors.

Modifying the microstructure of algae-based active carbon and modelling supercapacitors using artificial neural networks

An improved activated carbon material is synthesized from nostoc flagelliforme algae (NF) using an acid immersing method. The material has more pores and lower internal resistance compared with raw NF. Hydrofluoric acid can effectively decompose cellulose fibers and remove inorganic impurities, giving the carbon materials high mesopore volumes, which makes electrolyte ions rapidly transfer to the active site on the electrode surface. The specific capacitance of the sample was increased from 200 to 283 F g-1 after immersing in hydrofluoric acid. In addition, the symmetric supercapacitor shows an excellent energy density of 22 W h kg-1 at a power density of 80 W kg-1. The capacitance remains at 101.7% after 10 000 cycles. Furthermore, in order to find the relationship between the biochar structure and electrochemical performance in supercapacitors, an artificial neural network (ANN) method is used for studying the complex synergy mechanism. The specific capacitance is modelled using various input factors like aspect ratio (r L/D), cellulose ratio (CL(%)), specific surface area (S BET), pore volume (V tot), internal resistance (R s) and so on. The Levenberg-Marquart back propagation algorithm with sigmoid and ReLu active function is adopted to train the model. Random forest is used to analyse the relative importance of every input factor on specific capacitance. Results show that the model can estimate the energy storage with a mean squared error of 4.39 for materials with specific structure. Importance analyses indicate the first three significant variables are S BET, R s and V por. The ANN model can accurately predict the electrical properties of biomass-based carbon materials, and also provide guidance for the selection of energy storage materials in the future.

Recycled Carbon Fiber-Supported Polyaniline/Manganese Dioxide Prepared via One-Step Electrodeposition for Flexible Supercapacitor Integrated Electrodes

The exploration of multifunctional electrode materials has been a hotspot for the development of high-performance supercapacitors. We have used carbon fiber plates recovered from construction waste to prepare high-quality flexible carbon fiber materials by pyrolysis of epoxy resin. The as-prepared recycled carbon fiber has a diameter of 8 μm and is the perfect substrate material for flexible electrode materials. Furthermore, polyaniline and manganese dioxide are uniformly deposited on the recycled carbon fiber by one-step electrodeposition to form an active film. The recycled carbon fiber/polyaniline/MnO₂ composite shows an excellent specific capacitance of 475.1 F·g⁻¹ and capacitance retention of 86.1% after 5000 GCD cycles at 1 A·g⁻¹ in 1 M Na₂SO₄ electrolyte. The composites optimized for electrodeposition time have more electroactive sites, faster ions and electron transfer, structural stability and higher conductivity, endowing the composites promising application prospect.

‘Green Tide’ to Biochar: Preparation and Adsorption Isotherms for Three Typical Organic Pollutants

Enteromorpha prolifera (EP), the main source contributing to the outbreak of ‘green tide’, was used as the raw material to prepare biochars by pyrolysis. The biochars were analysed using N2-adsorption and Fourier transform infrared (FTIR) spectroscopy. The pyrolysis process was investigated by thermogravimetric analysis coupled with FTIR. The adsorption capacities of the biochars were compared in terms of removal efficiencies of methylene blue (MB), oxytetracycline (OTC) and humic acid (HA). The adsorption isotherms of the three organics by the optimum biochar were investigated. The results showed that the Brunauer–Emmett–Teller surface area of the biochar increased from 36 to 643 m2 g−1 with increasing pyrolysis temperature. The surface functional groups contained in EP were damaged during pyrolysis, while–N=O, S=O and C=N groups were formed on the biochar surface. Decomposition of EP resulted in the vigorous release of gaseous products at 240 °C, including CO2, H2O, aldehydes, ethers, aliphatic amines, sulfones and alcohols. CO2 was released due to the decomposition of carbonates above 700 °C and the in situ reduction of CO2 by carbon contained in the biochar was responsible for the high surface area of the biochar prepared at 750 °C (EPC750). EPC750 had the highest adsorption capacities for MB, OTC and HA among the biochars. The adsorption equilibrium data for MB and OTC onto EPC750 followed the Langmuir model with monolayer adsorption capacities of 138.89 and 103.31 mg g−1 respectively. The adsorption data for OTC also exhibited good agreement with the Freundlich model, suggesting the adsorption process was controlled by multiple mechanisms. The adsorption of HA by EPC750 followed the Freundlich model and the maximum adsorption capacity reached 64.27 mg g−1 under the experimental conditions.