A novel approach to environmental pollution management/remediation techniques using derived advanced materials

The carbon dioxide (CO2) crisis is one of the world's most urgent issues. Meeting the worldwide targets set for CO2 capture and storage (CCS) is crucial. Because it may significantly reduce energy consumption compared to traditional amine-based adsorption capture, adsorption dependant CO2 capture is regarded as one of the most hopeful techniques in this paradigm. The expansion of unique, critical edge adsorbent materials has received most of the research attention to date, with the main objective of improving adsorption capacity and lifespan while lowering the temperature of adsorption, thereby lowering the energy demand of sorbent revival. There are specific materials needed for each step of the carbon cycle, including capture, regeneration, and conversion. The potential and efficiency of metal-organic frameworks (MOFs) in overcoming this obstacle have recently been proven through research. In this study, we pinpoint MOFs' precise structural and chemical characteristics that have contributed to their high capture capacity, effective regeneration and separation processes, and efficient catalytic conversions. As prospective materials for the next generation of energy storage and conversion applications, carbon-based compounds like graphene, carbon nanotubes, and fullerenes are receiving a lot of interest. Their distinctive physicochemical characteristics make them suitable for these popular study topics, including structural stability and flexibility, high porosity, and customizable physicochemical traits. It is possible to precisely design the interior of MOFs to include coordinatively unsaturated metal sites, certain heteroatoms, covalent functionalization, various building unit interactions, and integrated nanoscale metal catalysts. This is essential for the creation of MOFs with improved performance. Utilizing the accuracy of MOF chemistry, more complicated materials must be built to handle selectivity, capacity, and conversion all at once to achieve a comprehensive solution. This review summarizes, the most recent developments in adsorption-based CO2 combustion capture, the CO2 adsorption capacities of various classes of solid sorbents, and the significance of advanced carbon nanomaterials for environmental remediation and energy conversion. This review also addresses the difficulties and potential of developing carbon-based electrodes for energy conversion and storage applications.

The Influence of Physical Mixing and Impregnation on the Physicochemical Properties of Pine Wood Activated Carbon Produced by One-Step ZnCl2 Activation

In this study, two different sample preparation methods to synthesize activated carbon from pine wood were compared. The pine wood activated carbon was prepared by mixing ZnCl₂ by physical mixing, i.e., "dry mixing" and impregnation, i.e., "wet mixing" before high temperature carbonization. The influence of these methods on the physicochemical properties of activated carbons was examined. The activated carbon was analyzed using nitrogen sorption (surface area, pore volume and pore size distribution), XPS, density, Raman spectroscopy, and electrochemistry. Physical mixing led to a slightly higher density carbon (1.83 g/cm³) than wet impregnation (1.78 g/cm³). Raman spectroscopy analysis also showed that impregnation led to activated carbon with a much higher degree of defects than physical mixing, i.e., I_D/I_G = 0.86 and 0.89, respectively. The wet impregnated samples also had better overall textural properties. For example, for samples activated with 1:1 ratio, the total pore volume was 0.664 vs. 0.637 cm³/g and the surface area was 1191 vs. 1263 m²/g for dry and wet mixed samples, respectively. In the electrochemical application, specifically in supercapacitors, impregnated samples showed a much better capacitance at low current densities, i.e., 247 vs. 146 F/g at the current density of 0.1 A/g. However, the physically mixed samples were more stable after 5000 cycles: 97.8% versus 94.4% capacitance retention for the wet impregnated samples.

One/Two-Step Contribution to Prepare Hierarchical Porous Carbon Derived from Rice Husk for Supercapacitor Electrode Materials

Grain processing generates vast amounts of agricultural byproducts, and biomass porous carbon electrode materials based on this have attracted broad research interests. Rice husk (RH) is one of the promising feedstocks owing to its good abundance and cheap price. Here, a RH-based porous carbon (RHPC) material was successfully prepared using first-step carbonization and second-step decalcification. The influence of carbonization temperature and decalcification treatment on the structure and electrochemical properties of the RH-based carbon materials were investigated. Thermogravimetric analysis, hydrogen element analysis, scanning electron microscopy, X-ray diffraction, and electrochemical performance tests were used to characterize and analyze the prepared RH-based carbon materials. After carbonization at 1000 °C (RH-1000) and decalcification treatment, RHPC-1000 showed the highest specific surface area of 643.48 m³/g and the largest pore volume of 0.52 cm³/g, which were about 1.8 times and 2.5 times that of RH-1000, respectively. RHPC-1000 also possessed a high capacitance retention capability of 97.2% after 10 000 charge-discharge cycles. The results demonstrated the excellent capacitive behavior and superior electrochemical performance of RHPC-1000. In summary, this study reveals a simple and effective preparation method of biomass porous carbon for supercapacitor electrode materials and provides new insight into the high-value utilization of waste biomass resources.

Application of δ-MnO2 and biochar materials in an arsenic-contaminated groundwater

Two activated biochar materials, peanut char (δ-MnO₂ /A-PC) and corn char (δ-MnO₂ /A-CC), were used to treat an arsenic solution containing 97.5% As(III) and 2.5% As(V). After reacting with δ-MnO₂ /A-PC for 24 h, 18.8% of As(III) and 35.4% of As(V) remained in the solution, revealing that some As(III) was oxidized to As(V) and the other was removed by adsorption. However, δ-MnO₂ /A-CC caused the solution to retain 15.6% of As(III) and 41.7% of As(V) under the same conditions, indicating that δ-MnO₂ /A-CC had higher oxidation for arsenic species than δ-MnO₂ /A-CC. Adsorption capacities for δ-MnO₂ /A-PC and δ-MnO₂ /A-CC to arsenic were 1.50 and 1.53 mg/g in a solution with 0.5 ppm As(III), respectively. After coating with δ-MnO₂ , the proportion of mesopore surface areas of δ-MnO₂ /A-CC increased from 33.3% to 79.0%, but their mesopore volumes increased from 67.6% to 89.4%. Fourier-transform infrared spectroscopy and X-ray diffraction analyses demonstrated that δ-MnO₂ was coated onto the surfaces of the biochars. The 600°C-ACC had a higher specific surface area, 221 m² /g, than the δ-600°C-APC, 81.5 m² /g; δ-MnO₂ /A-CC could attach more Mn (38.2%) than δ-MnO₂ /A-PC (27.8%). The elemental analysis revealed that δ-MnO₂ /A-PC and δ-MnO₂ /A-CC had similar carbon contents of 26.2%. PRACTITIONER POINTS: The δ-MnO₂ /biochar adsorbent can oxidize As(III) into As(V) in the groundwater. δ-MnO₂ /biochar adsorbed large amounts of As(III) and As(V). Adsorbent that contains more δ-MnO₂ has a higher oxidation capacity. The δ-MnO₂ /biochar made from corn stalks could combine with more δ-MnO₂ .

Multifunctional applications for waste zinc-carbon battery to synthesize carbon dots and symmetrical solid-state supercapacitors

In this study, we provide a simple and green approach to recycle waste zinc carbon batteries for making carbon dots and porous carbon material. The carbon dots are easily synthesized by one green step, the hydrothermal treatment of a carbon rod in a mixture of DI water and pure ethanol to obtain a blue fluorescence under UV light, which can be used directly as a fluorescence ink. The as-prepared carbon dot process give typical dots with a uniform diameter from 3 to 8 nm with a strong slight blue fluorescent. The porous carbon material is also recycled from carbon powder in a waste battery via one green step annealing process without any chemical activation and with a hierarchically porous structure. This porous carbon material is demonstrated as an electrode for symmetrical solid state supercapacitors (SSCs) in a sandwich structure: porous carbon/PVA-KOH/porous carbon. The SSCs using recycled porous carbon electrodes exhibit a good energy density of 4.58 W h kg-1 at a power density of 375 W kg-1 and 97.6% retention after 2000 cycles. The facile one green step of hydrothermal and also that of calcination provide a promising strategy to recycle waste zinc carbon batteries, which transfers the excellent applications.

Sonochemical assisted fabrication of 3D hierarchical porous carbon for high-performance symmetric supercapacitor

A scalable fabrication of 3D hierarchical porous carbon structure (3D-HPC) has been achieved via a simple sonochemical route at different pyrolysis temperatures. It is worth noting that all the 3D-HPC samples possess oxygen-functional groups after activation by KOH and self-doped by nitrogen, which are beneficial to improving their surface wettability as well as increasing the electro-active surface area between the electrode and the surrounding electrolyte, consequently enhancing their electrochemical performance. Remarkably, the resulting carbon sample pyrolyzed at 850 °C (AC-850) possesses a maximum doping level of 2.75 at% and a high surface area of 1376.19 m² g^-1, which exhibits high electrochemical performance with high capacitance up to 269.19 F g^-1 at a current density of 2 A g^-1. Moreover remarkably, the AC-850-based symmetric supercapacitor delivers a high energy density of 21.4 Wh kg^-1 at a power density of 531.2 W kg^-1 with excellent rate performance and superior cycling stability (94.7% retention over 5000 cycles). The present approach is very suitable for large scale production of high-quality porous carbon materials at low cost, which can be used in different aspects, such as energy storage, gas storage, environmental remediation, and so on.

Fabrication of Microcapsules by the Combination of Biomass Porous Carbon and Polydopamine for Dual Self-Healing Hydrogels

Artificial development of smart materials from agricultural waste or food residues is particularly desirable for green chemistry. In this paper, dual-network self-healing hydrogels were successfully fabricated by using functional microcapsules. These microcapsules were established by biomass porous carbon (PC) after recycling of apple residues. Glutaraldehyde (GA) as the healing agent was embedded in the porous carbon, and the outer surface was coated with polydopamine (PDA). After the microcapsules were added, modifying guar gum-type hydrogels were successfully obtained with dual self-healing performance by the combination of a healing agent and metal-ligand coordination. The self-healing efficiency was about 89.9% from the tension test, and the fracture strength was measured as 7.68 MPa. These results not only highlight a new idea for the utilization of apple residues but also provide a new method for the preparation of excellent self-healing hydrogels.

A high-performance asymmetric supercapacitor designed with a three-dimensional interconnected porous carbon framework and sphere-like nickel nitride nanosheets

The novel asymmetric supercapacitor was assembled based on a three-dimensional (3D) interconnected porous carbon framework as the negative electrode and 3D sphere-like nickel nitride nanosheets as the positive electrode in aqueous electrolyte.

Solvent-Free Mechanochemical Preparation of Hierarchically Porous Carbon for Supercapacitor and Oxygen Reduction Reaction

Hierarchically porous carbon (HPC) derived from fallen flowers was prepared by a green method of combining solvent-free ball milling with the safe activating agent potassium bicarbonate. By regulating the mass ratio of KHCO₃ to biochar, the as-prepared HPC materials possess high specific surface areas of up to 2147.9 m²  g^-1 and abundant hierarchical pores comprised of micro-, meso-, and macropores. The specific capacitances of the HPC materials are able to reach 302.7 F g^-1 at a current density of 0.5 A g^-1 in 6 m KOH, and the symmetric supercapacitor composed of two identical HPC electrodes shows good stability because 100 % of the specific capacitance is retained after 5000 charge/discharge cycles and 90.5 % of the specific capacitance remains after 12 000 cycles. Nitrogen self-doped HPC materials also show higher electrocatalytic activity and stronger methanol tolerance for the oxygen reduction reaction than that of the commercial Pt/C catalyst. This preparation method can be extended to the green conversion of other varieties of biomass waste into useful carbon materials.

Winter-jujube-derived carbon with self-doped heteroatoms and a hierarchically porous structure for high-performance supercapacitors

The synthesized JC samples possessed abundant self-doped heteroatoms and hierarchically porous structures (the co-existence of micro-, meso-, and macropores).