Sustainable Carbon Materials Research Articles

Manipulating the Optical Properties of Carbon Dots by Fine‐Tuning their Structural Features

As a new class of sustainable carbon material, "carbon dots" is an umbrella term covering many types of materials. Herein, a broad range of techniques was used to develop the understanding of hydrothermally synthesized carbon dots, and it is shown how fine-tuning the structural features by simple reduction/oxidation reactions can drastically affect their excited-state properties. Structural and spectroscopic studies found that photoluminescence originates from direct excitation of localized fluorophores involving oxygen functional groups, whereas excitation at graphene-like features leads to ultrafast phonon-assisted relaxation and largely quenches the fluorescent quantum yields. This is arguably the first study to identify the dynamics of photoluminescence including Stokes shift and allow the relaxation pathways in these carbon dots to be fully resolved. This comprehensive investigation sheds light on how understanding the excited-state relaxation processes in different carbon structures is crucial for tuning the optical properties for any potential commercial applications.

Cover Feature: Preparation of Biomass‐Based Porous Carbons with High Specific Capacitance for Applications in Supercapacitors (ChemElectroChem 14/2019)

The Cover Feature depicts a sustainable high-performance carbon material for supercapacitors prepared through the simple and green thermal pyrolysis of orange peel as the raw material and KOH as an activator. The prepared supercapacitors show that the hierarchical porous carbon with ultrathin graphene-like sheets offer excellent electrochemical performance. More information can be found in the Article by H. Shen et al. on page 3599 in Issue 14, 2019 (DOI: 10.1002/celc.201900395).

Carbon Nanosheet Frameworks Derived from Pine Cone Shells as Sodium-Ion Battery Anodes

As a kind of green, environment-friendly and sustainable carbon material, biomass carbon has simple processing technology and undoubtedly been the best candidate for industrialization. Different activation processes can be used to change the internal microstructure of carbons, and design pores that facilitate ions transport and electrons conduction, thereby achieving the ultimate goal of improving electrochemical performance. Herein, we select the same activator (KOH) and activation time (3 h) but change the activation temperature (300 °C, 600 °C, 800 °C) to obtain biomass-derived carbon with the different micromorphology, pores structure and heteroatoms content. Rather, We choose ether-based electrolyte, due to its highly reversible graphite co-intercalation reaction, the problem of extremely low electrochemical activity of graphite in ester electrolytes is avoided. Results indicate, the sample PCS-600 exhibites sheet structure with specific surface area of 38.3 m2/g and large average pore width of 2.77 nm, which providing sufficient conditions for ions transport. PCS-600 has 1.05 at% N and 5.75 at% O heteroatoms, which providing additional pseudocapacitance. In addition, the electrochemical performance of PCS-600 is optimal, at a current density of 0.1 A/g, its specific capacity is 198.6 mA h/g, maintain at ~95% after 100 cycles, with coulomb efficiency ~100%.

Sustainable Porous Carbon Materials Derived from Wood-Based Biopolymers for CO₂ Capture.

Porous carbon materials with tunable porosities and functionalities represent an important class of CO2 sorbents. The development of porous carbons from various types of biomass is a sustainable, economic and environmentally friendly strategy. Wood is a biodegradable, renewable, sustainable, naturally abundant and carbon-rich raw material. Given these advantages, the use of wood-based resources for the synthesis of functional porous carbons has attracted great interests. In this mini-review, we present the recent developments regarding sustainable porous carbons derived from wood-based biopolymers (cellulose, hemicelluloses and lignin) and their application in CO2 capture.

Sustainable Graphitic Carbon Materials from Biogas as Anodes for Sodium-Ion Batteries

Novel graphitic materials of renewable origin, biogas-derived carbon nanofibers (BCNFs), are investigated as anodes for sodium-ion batteries in a glyme-based electrolyte. These materials show a unique combination of electrochemical properties, including suitable capacity (∼100 mAh g−1), high rate capability, excellent cycle stability and coulombic efficiency as well as long cycle life (∼6000 cycles up to 7.5 A g−1) which make them adequate candidates for this application. The sodiation of BCNFs occurs through different combinations of diffusion-controlled intercalation and capacitive intercalation processes. Overall, the quantitative contribution of the capacitive current to the total stored sodium in BCNF electrodes is noteworthy (28–71%), which account for their ultrahigh rate performance, comparable to that of supercapacitors, because of the improvement of the transportability of the Na+ ions through the graphene layers.

Robust hierarchically interconnected porous carbons derived from discarded Rhus typhina fruits for ultrahigh capacitive performance supercapacitors

An efficient and economic approach for sustainable production of hierarchically interconnected porous carbons are designed and fabricated through the pyrolysis of Rhus typhina fruits and followed by KOH activation to create micropores or mesopores on the nano-sheet wall of macropores. The related N-doped carbon consists of a plenty of micropores and owns high specific surface area (up to 2675 m2 g−1), resulting in high performances for supercapacitors, such as ultrahigh specific capacitance (568 F g−1 at 1 A g−1), remarkable rate capability (310 F g−1 at 20 A g−1, 282 F g−1 at even 30 A g−1 current density) and good long-term stability (capacitance retention of 99% after 10000 cycles at 30 A g−1) in 1 mol L−1 H2SO4. Moreover, the carbon derived from Rhus typhina fruits demonstrates 474 F g−1 at 1 A g−1, 281 F g−1 at 30 A g−1, and capacitance retention of 92% after 10000 cycles at 30 A g−1 in 6 mol L−1 KOH electrolyte. This novel and sustainable biomass-derived carbon material holds a bright future for fabricating high energy supercapacitors.

Development and Evaluation of a Sustainable Long-release Carbon Material Applied for In-Situ Remediation of Groundwater Nitrogen Pollution

Due to slow flow rates and inter-substance reactions in groundwater, remediation requires the addition of materials with sustained release properties. This research uses agricultural waste and zero-valent iron (Fe0), coupling biology and chemistry, to research and develop a sustainable long-release carbon material with a synergistic physico-habitat, and to evaluate its performance, also taking into account the occurrence of nitrogen in groundwater. The material developed has a double-layer structure with an inner core and an outer shell. The core, consisting of agricultural waste, Fe0, and other raw materials, constitutes the repair layer. Agricultural waste provides a carbon source for microorganisms, and Fe0 can quickly remove nitrate via chemical reactions and reduce DO to develop an anaerobic environment in water. The shell provides a solute permeation layer and consists of primary minerals and other components. This can slow the release of TOC from the core and adsorb secondary contaminants. Physical properties testing showed that the materials core was uniformly cross-linked, and its shell exhibited a clear uniform pore structure (SEM). Favorable mechanical compression was recorded for particle strengths of up to 80-105 N. With a density of 1.1 g·cm-3, the material did not float in water. Experiments showed that the material had excellent sustained release. The amount[Max:21-25 mg·(g·L)-1] and rate[Max:0.185 mg·(g·L·d)-1] of TOC release exhibited a steady state trend, but fluctuated greatly in the case of agricultural wastes[(Max amount:53-75 mg·(g·L)-1, Max rate:0.455 mg·(g·L·d)-1]. In terms of further functional gene abundance, materials leachate was found to be conducive to denitrifying bacteria. In early denitrification and oxygen trapping experiments, the Fe0 chemical reaction was dominant for reduction of nitrogen and DO, facilitating denitrification. However, biological denitrification gradually dominated. Differences in denitrification rates between iron-free and iron-containing materials were smaller, as was the correlation between denitrification rate and iron content. These results indicate the formation of physico-habitat synergistic denitrification in the materials system.

Metal-Organic Framework Supported on Food Waste-Derived Carbon As an Efficient Bifunctional Catalyst for Oxygen Electrocatalysis

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are a core pair in many energy storage and conversion systems, such as regenerative fuel cells and rechargeable metal-air batteries. Unfortunately, both reactions possess sluggish kinetics, involving multiple charge-/proton-transfers and oxygen bond breaking (in ORR)/recombining (in OER) processes at the “solid-liquid-gas” triple phase interfaces. Therefore efficient bifunctional catalysts are urgently needed. The most efficient oxygen-relative electrocatalysts are made from precious metal, but there is no a single catalyst based on precious metals that can serve the need for both ORR and OER. Metal-organic frameworks (MOFs) are porous crystalline materials self-assembled with metal nodes and organic linkers with various compositions, high specific surface areas, tunable pore structures, and easily functionalized. Therefore, MOFs have provided opportunities for advancements in oxygen electrocatalysis. MOFs-based ORR/OER electrocatalysts are generally used in two ways: (1) by self-sacrificing through pyrolysis, and (2) in pristine phases. The former is at the expense of MOFs’ properties, while the latter falls short of meeting the practical target due to the poor conductivity of pristine MOFs, requiring carbon support. Conventional carbon supports are synthesized from fossil fuel precursors with harsh synthetic conditions and high energy consumption. Sustainable carbon materials should be derived from renewable resources (especially agriculture/food waste), and the preparation process should be green, facile and easy to scale up. Herein, a Co(mIm)2 (mIm=methyl-imidazole) MOF was incorporated with N-doped pomelo-peel-derived carbon (NPC) as a synergistic ORR/OER bifunctional catalyst in an alkaline electrolyte (Fig. 1A). Through rotating disk electrode voltammetry, an optimized composite exhibits an ORR/OER overpotential gap, ΔE (E OER@10 mAcm-2-E ORR@-1 mAcm-2), as small as 0.79V (Fig. 1B), putting the catalyst among the best of the reported bifunctional electrocatalysts so far. The catalyst also demonstrated a 4-electron transfer pathway and superior catalytic stability. The Co-N4 ligation in MOF, electrochemical active surface area, and the strong interactions between MOF and support are attributed as the main contributors to the bifunctional catalytic activity. These factors act synergistically, resulting in substantially enhanced bifunctional catalytic activity and stability. Figure 1

Fungus-derived photoluminescent carbon nanodots for ultrasensitive detection of Hg2+ ions and photoinduced bactericidal activity

Abstract Herein, we present a sustainable solvent-free synthetic procedure to produce carbon nanodots from common edible mushrooms (Pleurotus spp.). The resulting mushroom carbon nanodots (MCDs) exhibit stable blue fluorescence with high quantum yield (25%). The MCDs are highly dispersible in water because of the enormous number of oxygen- and nitrogen-containing functional groups on the surface. The MCDs can be used as an effective fluorescent probe for label-free detection of Hg2+ ions (detection limit: 4.13 nM). To improve the sensitivity, dihydrolipoic acid was attached to the surface of MCDs, resulting in ultra-sensitivity in Hg2+ ion sensing, with a detection limit as low as 17.4 pM. In addition, the MCDs can be used for the labeling of bacteria and as a photoinduced bactericidal agent. Light irradiation of E. coli treated with MCDs showed excellent bactericidal activity relative to the control. These sustainable and affordable carbon materials are potentially compatible for monitoring toxic metals and as a potent visible-light-responsive bactericidal probe.

The porous carbon derived from water hyacinth with well-designed hierarchical structure for supercapacitors

A hierarchical porous water hyacinth-derived carbon (WHC) is fabricated by pre-carbonization and KOH activation for supercapacitors. The physicochemical properties of WHC are researched by scanning electron microscopy (SEM), N2 adsorption-desorption measurements, X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results indicate that WHC exhibits hierarchical porous structure and high specific surface area of 2276 m2/g. And the electrochemical properties of WHC are studied by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) tests. In a three-electrode test system, WHC shows considerable specific capacitance of 344.9 F/g at a current density of 0.5 A/g, good rate performance with 225.8 F/g even at a current density of 30 A/g, and good cycle stability with 95% of the capacitance retention after 10000 cycles of charge-discharge at a current density of 5 A/g. Moreover, WHC cell delivers an energy density of 23.8 Wh/kg at 0.5 A/g and a power density of 15.7 kW/kg at 10 A/g. Thus, using water hyacinth as carbon source to fabricate supercapacitors electrodes is a promising approach for developing inexpensive, sustainable and high-performance carbon materials. Additionally, this study supports the sustainable development and the control of biological invasion.

Biomass-Derived Carbon Nanospheres with Turbostratic Structure as Metal-Free Catalysts for Selective Hydrogenation of o-Chloronitrobenzene

Nowadays, metal-free catalysts are sought after for synthesis of fine chemicals. Herein, we utilized the natural biomass xylose as the precursor to fabricate carbon nanospheres with turbostratic carbon structure via hydrothermal treating and high-temperature calcinating. These green and sustainable carbon materials were used as metal-free catalysts in selective hydrogenation of o-chloronitrobenzene (o-CNB), exhibiting a significantly enhanced catalytic activity with the increasing calcination temperature, as well as 100% selectivity to o-chloroanilines (o-CAN). In terms of the systematic characterization and simulated calculation, it is found turbostratic carbon formed in the calcination process might act as the catalytic active center in this reaction, and its selective reaction with −NO2 in o-CNB results in the enhanced catalytic activity and fully selectivity to o-CAN.

Coniferous pine biomass: A novel insight into sustainable carbon materials for supercapacitors electrode

Low-cost biomass-derived activated porous carbon from natural pine cones is synthesized using hydrothermal approach followed by KOH activation and carbonization. The produced carbon materials have a high surface area of 1515 m2 g−1 with a well-developed meso/micropores structure which is advantageous and favorable for mass transfer and ion accommodation for fast rate performance by providing pathways for electrolyte permeation and contact probability. Symmetric device fabricated using the obtained carbon material as electrode, exhibited good electrochemical performance with no degradation of capacitance after voltage holding at 1 V for about 60 h demonstrating good rate capability of the fabricated device. The results demonstrate the exciting potential of the pine cone derived carbons as a promising candidate for high-performance electrode materials for supercapacitors if fully explored.

Polyurethane Foam-Based Ultramicroporous Carbons for CO2 Capture.

A series of sustainable porous carbon materials were prepared from waste polyurethane foam and investigated for capture of CO2. The effects of preparation conditions, such as precarbonization, KOH to carbon precursor weight ratio, and activation temperature, on the porous structure and CO2 adsorption properties were studied for the purpose of controlling pore sizes and nitrogen content and developing high-performance materials for capture of CO2. The sample prepared at optimum conditions shows CO2 adsorption capacities of 6.67 and 4.33 mmol·g(-1) at 0 and 25 °C under 1 bar, respectively, which are comparable to those of the best reported porous carbons prepared from waste materials. The HCl treatment experiment reveals that about 80% of CO2 adsorption capacity arises from physical adsorption, while the other 20% is due to the chemical adsorption originated from the interaction of basic N groups and CO2 molecules. The relationship between CO2 uptake and pore size at different temperatures indicates that the micropores with pore size smaller than 0.86 and 0.70 nm play a dominant role in the CO2 adsorption at 0 and 25 °C, respectively. It was found that the obtained carbon materials exhibited high recyclability and high selectivity to adsorption of CO2 from the CO2 and N2 mixture.

Activated carbons with high nitrogen content by a combination of hydrothermal carbonization with activation

This paper reports the production of carbons materials with a nitrogen content around 8%(w/w) and a well-developed porous structure, with BET surface area and pore volume up to 2130 m2 g−1 and 1.12 cm3 g−1, respectively, produced by a combination of hydrothermal carbonization, an environmental friendly method in the production of sustainable tunable carbon materials, with traditional activation methods. The porosity was developed through an activation process according to different routes, namely activation with CO2 and chemical activation using CaCO3 and K2CO3. The successful production of activated carbons using chitosan as a nitrogen source revealed to be a good alternative to post-synthesis methods.

Development of Biochar-Based Functional Materials: Toward a Sustainable Platform Carbon Material.

Development of Biochar-Based Functional Materials: Toward a Sustainable Platform Carbon Material.

Synthesis of High‐Surface‐Area Nitrogen‐Doped Porous Carbon Microflowers and Their Efficient Carbon Dioxide Capture Performance

Sustainable carbon materials have received particular attention in CO2 capture and storage owing to their abundant pore structures and controllable pore parameters. Here, we report high-surface-area hierarchically porous N-doped carbon microflowers, which were assembled from porous nanosheets by a three-step route: soft-template-assisted self-assembly, thermal decomposition, and KOH activation. The hydrazine hydrate used in our experiment serves as not only a nitrogen source, but also a structure-directing agent. The activation process was carried out under low (KOH/carbon=2), mild (KOH/carbon=4) and severe (KOH/carbon=6) activation conditions. The mild activated N-doped carbon microflowers (A-NCF-4) have a hierarchically porous structure, high specific surface area (2309 m(2) g(-1)), desirable micropore size below 1 nm, and importantly large micropore volume (0.95 cm(3) g(-1)). The remarkably high CO2 adsorption capacities of 6.52 and 19.32 mmol g(-1) were achieved with this sample at 0 °C (273 K) and two pressures, 1 bar and 20 bar, respectively. Furthermore, this sample also exhibits excellent stability during cyclic operations and good separation selectivity for CO2 over N2.

Sustainable carbon materials.

Carbon-based structures are the most versatile materials used in the modern field of renewable energy (i.e., in both generation and storage) and environmental science (e.g., purification/remediation). However, there is a need and indeed a desire to develop increasingly more sustainable variants of classical carbon materials (e.g., activated carbons, carbon nanotubes, carbon aerogels, etc.), particularly when the whole life cycle is considered (i.e., from precursor "cradle" to "green" manufacturing and the product end-of-life "grave"). In this regard, and perhaps mimicking in some respects the natural carbon cycles/production, utilization of natural, abundant and more renewable precursors, coupled with simpler, lower energy synthetic processes which can contribute in part to the reduction in greenhouse gas emissions or the use of toxic elements, can be considered as crucial parameters in the development of sustainable materials manufacturing. Therefore, the synthesis and application of sustainable carbon materials are receiving increasing levels of interest, particularly as application benefits in the context of future energy/chemical industry are becoming recognized. This review will introduce to the reader the most recent and important progress regarding the production of sustainable carbon materials, whilst also highlighting their application in important environmental and energy related fields.

Hierarchical porous carbonaceous materials via ionothermal carbonization of carbohydrates

We report on the ionothermal synthesis of porous carbon materials from a variety of carbohydrate precursors (i.e.D-glucose, D-fructose, D-xylose, and starch) using 1-butyl-3-methylimidazolium tetrachloroferrate(III), [Bmim][FeCl4] as a reusable solvent and catalyst. The carbon materials derived from these different carbohydrates are similar in terms of particle size and chemical composition, possessing relatively high surface areas from 44 to 155 m2 g−1 after ionothermal processing, which can be significantly increased to >350 m2 g−1 by further thermal treatment (e.g. post-carbonization at 750 °C). CO2 and N2 sorption analysis, combined with Hg intrusion porosimetry, reveals a promising hierarchical pore structuring to these carbon materials. The ionic liquid [Bmim][FeCl4] has a triple role: it acts as both a soft template to generate the characterized pore structuring, solvent and as a catalyst resulting in enhanced ionothermal carbon yields. Importantly from a process point of view, the ionic liquid can be successfully recovered and reused. The current work shows that ionothermal synthesis has the potential to be an effective, low cost, and green reusable synthetic route towards sustainable porous carbon materials.

Chemistry and materials options of sustainable carbon materials made by hydrothermal carbonization

The production of functional nanostructured materials starting from cheap natural precursors using environmentally friendly processes is a highly attractive subject in material chemistry today. Recently, much attention has been focused on the use of plant biomass to produce functional carbonaceous materials, encompassing economic, environmental and social issues. Besides the classical route to produce activated carbons from agricultural side products, the hydrothermal carbonization (HTC) process shows clear advantages in that it can generate a variety of cheap and sustainable carbonaceous materials with attractive nanostructure and functionalization patterns for a wide range of applications. In this tutorial review we present the latest developments in this traditional but recently invigorated technique. It will be shown that HTC does not only access carbonaceous materials under comparatively mild hydrothermal conditions, but also replaces the more technical and structurally well-defined charring by a controlled chemical process. It will be shown that this makes it possible to tailor the final structure with the tools of colloid and polymer science, leading to very different morphologies with miscellaneous applications, including modern carbon nanocomposites and hybrids.