Oxygen-rich Functional Groups Research Articles

Activated Graphite with Richly Oxygenated Surface from Spent Lithium-Ion Batteries for Microwave Absorption.

Designing spent graphite anodes from lithium-ion batteries (LIBs) for applications beyond regenerated batteries offers significant potential for promoting the recycling of spent LIBs. The battery-grade graphite, characterized by a highly graphitized structure, demonstrates excellent conductive loss capabilities, making it suitable for microwave absorption. During the Li-ion intercalation and deintercalation processes in battery operation, the surface layer of spent graphite (SG) becomes activated, forming oxygen-rich functional groups that enhance the polarization loss mechanism. To further control the polarization loss and achieve optimized impedance matching, reduced graphene oxide (rGO) is employed as a modifier. Herein, rGO serves as a binder, effectively combining individual SG particles. The matched Fermi levels of SG and rGO reduce the interfacial barrier, facilitating rapid electron transfer. Simultaneously, their combination forms a 3D conduction network, which not only enhances multiple scattering, reflection, and attenuation of electromagnetic waves but also provides abundant polarization centers for increased microwave absorption. As a result, the optimized SG/rGO aerogel achieves an impressive effective absorption bandwidth of 7.04GHz and accompanied by a minimum reflection loss of -51.1dB. This study broadens the scope of spent LIBs utilization and provides insights for wilder and more functional applications.

In-situ electrochemical XRD and raman probing of ion transport dynamics in ionic liquid-etched Ti3C2Tx MXene for energy storage applications

This study focuses on understanding the electrochemical behavior of Ti3C2Tx MXene synthesized using tetramethylammonium tetrafluoroborate (TMATFB) as an etching agent for the Ti3AlC2 MAX phase. Through in situ Raman spectroscopy and X-ray diffraction (XRD), we investigate the charge storage mechanisms and surface transformations of TMATFB-etched MXene. The results indicate that Ti3C2Tx MXene undergoes reversible H+ ion intercalation, achieving a specific capacitance of 417.4F/g at 1 mV/s in 1 M H2SO4. This reversible process is characterized by a transformation between Ti3C2O2 and Ti3C2(OH)2 on the MXene surface, highlighting the role of oxygen-rich functional groups in enhancing pseudocapacitive behavior. These insights contribute to the understanding of MXene’s electrochemical potential in energy storage systems.

Sensitive Detection of Hg2+ and l-Cysteine through Optical Asymmetry-Tuned Fluorescence Switch Off-On Behavior in N-Doped Chiral Carbon Dot.

Blue-emissive nitrogen-doped chiral carbon dots (d-NCD230 and l-NCD230) exhibiting antipodal chiroptical activity, synthesized from the thermal pyrolysis of citric acid and d/l-aspartic acid in 1:2 molar ratios, have been explored as chirality-based fluorescent turn-off/on probes for the detection of Hg2+ and l-cysteine (l-Cys). Circular dichroism (CD) spectroscopy revealed that the chiroptical activity originates from a synergy among intrinsic chirality, chiral precursors on the NCD surface, and hybridization of lower energy levels within the embedded chiral chromophore. Quantitative analysis of optical asymmetry using the Kuhn asymmetry factor (g) at the CD signal of 312 nm showed a higher value for d-NCD230 (1.03 × 10-4) compared to l-NCD230 (1.13 × 10-5). Moreover, we have demonstrated chirality transfer and chiral inversion phenomena in d/l-NCDs by preparing carbon dots with different precursor ratios at different temperatures and probing them through CD spectroscopy. The NCDs exhibited selective fluorescence quenching in the presence of Hg2+, demonstrating linearity in the Stern-Volmer plot. Limits of detection (LODs) for Hg2+ were calculated to be 129 and 192 nM for d-NCD230 and l-NCD230, respectively, in the 0-150 μM concentration range. The quenching mechanism involves nonradiative electron transfer due to Hg2+ binding to oxygen-rich functional groups on the d/l-NCD230 surface. The slight variation in LOD values between d-NCD230 and l-NCD230 indicates the negligible effect of the chirality on Hg2+ sensing. Notably, the fluorescence intensity of d/l-NCD230 could be restored upon adding l-cysteine, with d-NCD230 showing a more pronounced enhancement than l-NCD230. This differential response is attributed to a preferential stereoselective interaction arising from the homochirality of d-NCD230/Hg2+ and l-cysteine. These findings demonstrate the potential of chiral nitrogen-doped carbon dots as sensitive and selective probes for Hg2+ and l-cysteine, with implications for environmental monitoring and biological sensing applications.

Jackfruit waste derived oxygen-self-doped porous carbon for aqueous Zn-ion supercapacitors

To fully harness the benefits of high energy density, strategic fabrication of hierarchical porous carbon (PC) materials is essential and highly impactful. In this study, oxygen-self-doped PC materials are synthesized from jackfruit waste (JK) through pyrolysis combined with chemical activation. The resulting material (JKPC-4) features abundant interfacial active sites and a short ions/electrons transfer distance, enhancing the ion adsorption capacity and kinetic behavior of the cathode. Additionally, the oxygen-rich functional groups contribute to increased pseudocapacitance and enhance the wettability and conductivity of the material. Consequently, the assembled JKPC-4//JKPC-4 symmetric supercapacitor in 2M Na2SO4 electrolyte exhibits a high energy density of 36.06 Wh kg−1 at 647.94 W kg−1. Furthermore, the JKPC-4//Zn device demonstrates a notable capacity of 225 mAh g−1 at 0.1 A g−1, exceptional rate capability (93 mAh g−1 at 10 A g−1), high energy density (154 Wh kg−1), and impressive cycle stability, retaining 97 % of its capacity after 10,000 cycles at 10 A g−1. The electrochemical process is studied using ex-situ characterization. Mechanistic studies have shown that the outstanding energy storage capability and charge-transfer processes of JKPC-4 stem from the synergistic interplay between oxygen heteroatoms and suitable pore structure.

Competitive adsorption of H2O and CO2 on nitrogen-doped biochar with rich-oxygen functional groups

Since fossil-fuel power plants emit humid flue gases, the competitive adsorption of CO2 with H2O is inevitable for adsorptive carbon capture technologies. Nitrogen- and oxygen-containing functional groups can enhance adsorption capacity and selectivity of biochar. However, the interaction between N/O functional groups and CO2 in the presence of H2O is not clarified. In this study, a series of nitrogen-doped biochars rich in oxygen-containing functional groups were synthesized using a facile method. The N-doping enhanced the CO2 sorption as the best sample showed a sorption uptake of 1.21 mmol/g at 25 °C and 15 vol% CO2 (balanced with N2). The saturated sorption amounts of CO2, H2O, and N2 followed the order:qH2O(8.27 mmol/g)>qCO2(1.82 mmol/g) ≫qN2 (0.12 mmol/g). In CO2/H2O co-adsorption, CO2 sorption of the N-doped biochar was reduced only by 28.7 %. Therefore, sorption of H2O was more preferred than CO2 in terms of equilibrium; meanwhile, the sorption of H2O was restricted by slow kinetics. DFT simulations suggested that, except for quaternary nitrogen, the N/O functional groups increased the adsorption energies of CO2 and H2O and the adsorption energies of H2O were higher than those of CO2 (e.g. CO2 and H2O with pyridine-N were −26.47 and −34.53 kJ/mol, respectively), because N/O doping changed the polarity of biochar surface. The current study can improve the understanding of the competitive sorption of CO2 and H2O on N/O doped biochar, facilitating biochar application for CO2 capture from humid flue gas.

Construction of Chitosan-biochar/ZnO/NiO composites for efficient photocatalytic removal of Congo red and tetracycline

The combination of photocatalyst and biochar is an effective strategy to improve the overall photocatalytic activity, but it is still a challenge to find photocatalyst with excellent photocatalytic activity and biochar with large surface and rich oxygen functional groups. In this study, a novel CS-biochar/ZnO/NiO composite with adsorption-photocatalytic performance was constructed using chitosan as biochar source, and exploited for visible-light-driven photocatalytic degradation of tetracycline (TC) and Congo red (CR). The superior photocatalytic activity of CS-biochar/ZnO/NiO than pristine ZnO, NiO and CS-biochar/ZnO under visible light, and 63 %-CS/ZnO/NiO composite has the best photocatalytic activity. The photodegradation efficiency for CR was 94.5 % within 100 min, and the apparent rate constant (k) was 0.0206 min−1, which is about 1.87 and 3.89 times that ZnO and NiO, respectively. For TC, the photodegradation efficiency was 90 % within 45 min, and k was 0.0377 min−1, which is about 1.74 and 2.86 times that bare NiO and ZnO, respectively, which attribute to the synergistic effect between ZnO/NiO and CS-biochar improved the activity of photocatalysts. This work presents a straightforward approach for improving photocatalytic antibiotic and dye degradation through the construction of bifunctional "hybrid" material, which have great potential for application in the removal of contaminants.

Plant extract mediated in-situ synthesis of iron/manganese alginate hydrosphere and its excellent recovery of rare earth elements in mine wastewater

The recovery of rare earth elements (REEs) is a major issue based on environmental governance and sustainable resource utilization. In this study, we developed a novel hydrogel material (Fe/Mn@ALG) by anchoring Fe/Mn NPs on alginate spheres, where Fe/Mn NPs were in-situ synthesized using Euphorbia cochinchensi leaf extract as reduced and protection agents. The Fe/Mn@ALG was applied directly to real mine wastewater, generating efficient and selective recovery of REEs with the coexistence of numerous competing metal ions. As results have shown, Fe/Mn@ALG was a useful adsorbent for REEs with an adsorption efficiency 78.62 % achieved, which was also confirmed by distribution coefficients (Kd), up to 2451.66 mL·g−1. Furthermore, Fe/Mn@ALG exhibited preferential response to REEs over other metal ions with the separation factor (SF) being up to 240. This great adsorption performance and selectivity toward REEs were attributed to its specific surface area, oxygen-rich functional groups and negatively charged surface in acid wastewater. Furthermore, REEs could be greatly desorbed from Fe/Mn@ALG with output concentration being three times higher than the initial concentration. Additionally, Fe/Mn@ALG maintained its good adsorption performance with efficiency reaching 72.24 % after five reuses. Overall, Fe/Mn@ALG can be considered as a promising candidate for wastewater remediation and sustainable management of resources.

Production of hydrochar from the hydrothermal carbonisation of food waste feedstock for use as an adsorbent in removal of heavy metals from water

AbstractIn this research, discarded butternut peels were converted into hydrochar products through hydrothermal carbonisation (HTC), with adjustments made to the temperature (ranging from 180 to 260℃) and residence time (spanning 45–180 min). The findings indicated that both the temperature and time of carbonisation significantly influenced the yield of hydrochar (HC), as well as its physiochemical and structural properties. Higher temperatures and prolonged residence time led to decreased yield, elevated fixed carbon content and an increased fuel ratio. Furthermore, raising the process conditions increased HHV and reduced the oxygen-containing functional groups. The HC yield dropped from 28.75 to 17.58% with increased carbonisation temperature and time. The findings of this study also suggest that modified hydrochar is a promising material for removing heavy metals from wastewater. It is a relatively low-cost and abundant material that can be produced from various biomass feedstocks, including food waste. In addition, it is a sustainable and environmentally friendly option for wastewater treatment. Hydrochar-based systems offer several advantages over traditional methods of heavy metal removal, such as chemical precipitation and ion exchange. The unique physicochemical characteristics of hydrochar, including its porous structure and oxygen-rich functional groups, offer a high surface area and more binding sites for heavy metal ions. By changing the physicochemical properties of hydrochar with chemicals like phosphoric acid, it is possible to increase its adsorption capacity. The Freundlich isotherm was the best fit for the adsorption data for all three metal ions (Pb2+, Cu2+ and Cd2+), indicating that the adsorption process is multilayer and heterogeneous.

Binding between Cu2+/Zn2+ and aged polyethylene and polyethylene terephthalate microplastics in swine wastewaters: Adsorption behavior, and mechanism insights

Microplastics (MPs) have aroused growing environmental concerns due to their biotoxicity and vital roles in accelerating the spread of toxic elements. Illuminating the interactions between MPs and heavy metals (HMs) is crucial for understanding the transport and fate of HM-loaded MPs in specific environmentally relevant scenarios. Herein, the adsorption of copper (Cu2+) and zinc (Zn2+) ions over polyethylene (PE) and polyethylene terephthalate (PET) particulates before and after heat persulfate oxidation (HPO) treatment was comprehensively evaluated in simulated and real swine wastewaters. The effects of intrinsic properties (i.e., degree of weathering, size, type) of MPs and environmental factors (i.e., pH, ionic strength, and co-occurring species) on adsorption were investigated thoroughly. It was observed that HPO treatment expedites the fragmentation of pristine MPs, and renders MPs with a variety of oxygen-rich functional groups, which are likely to act as new active sites for binding both HMs. The adsorption of both HMs is pH- and ionic strength-dependent at a pH of 4–6. Co-occurring species such as humic acid (HA) and tetracycline (TC) appear to enhance the affinity of both aged MPs for Cu2+ and Zn2+ ions via bridging complexation. However, co-occurring nutrient species (e.g., phosphate and ammonia) demonstrate different impacts on the adsorption, improving uptake of Cu2+ by precipitation while lowering affinity for Zn2+ owing to the formation of soluble zinc-ammonia complex. Spectroscopic analysis indicates that the dominant adsorption mechanism mainly involves electrostatic interactions and surface complexation. These findings provided fundamental insights into the interactions between aged MPs and HMs in swine wastewaters and might be extended to other nutrient-rich wastewaters.

Enhancing solid-phase extraction of tetracyclines with a hybrid biochar sorbent: A comparative study of chlorella and bamboo biochars

Biochar, a sustainable sorbent derived from pyrolyzed biomass, has garnered attention for its efficacy in solid-phase extraction (SPE) of antibiotics, with a particular focus on tetracyclines (TCs). Despite its recognized potential, the intricate separation mechanisms operative in biochar-based SPE systems have not been fully deciphered. This investigation contrasts chlorella biochar against commercial bamboo biochar, harnessing an array of analytical methodologies-microstructure characterization, adsorption thermodynamics, competitive adsorption kinetics, H+ back titration, and selectivity adsorption studies-complemented by a Box-Behnken design for the optimization of chlorella/bamboo-SPE and subsequent application in the analysis of animal-derived foodstuffs. The study unveils that a hybrid sorbent, integrating nitrogen-doped microporous chlorella biochar with mesoporous bamboo biochar in a 95/5 mass ratio, markedly diminishes irreversible adsorption while enhancing selectivity, surpassing the performance of single biochar SPE systems. The elucidated separation mechanisms implicate a partition model, propelled by oxygen-rich functional groups on chlorella biochar and the rapid adsorption kinetics of bamboo biochar, all orchestrated by electrostatic interactions within the mixed biochar framework. Moreover, the synergy of mixed biochar-SPE with high-performance liquid chromatography (HPLC) demonstrates exceptional proficiency in detecting TCs in animal viscera, evidenced by recovery rates spanning 80.80 % to 106.98 % and RSDs ranging from 0.24 % to 14.69 %. In essence, this research not only sheds light on the multifaceted factors influencing SPE efficiency but also propels the use of biochar towards new horizons in environmental monitoring and food safety assurance.

High-load Ti3C2 MXene cathode through surface modification for degradable aqueous zinc-ion micro-supercapacitors with excellent energy density and anti-self-discharge

Micro Zn-ion supercapacitors (MZSCs) with excellent power density and safety are considered the most promising micro-energy storage devices. However, the energy density per unit area of these devices is insufficient to meet the requirements for portable/wearable electronics. Furthermore, traditional energy storage devices produce a large amount of e-waste, causing serious environmental hazards. To solve these problems, degradable MZSCs are proposed based on high-load surface-modified MXene (O-Ti3C2 MXene) cathodes and Zn/carbon nanotube (CNT) anodes. Owing to the advantages of their three-dimensional interconnected microstructures and abundant oxygen-rich functional groups, the thick O-Ti3C2 MXene electrodes show high rate performances and excellent Zn2+ diffusion kinetics. Therefore, MZSCs exhibit an extremely high energy density (384.90 μWh cm−2 at 0.30 mW cm−2) and power density (6.0 mW cm−2 at 126.84 μWh cm−2) and are degradable. More importantly, because of the strong adsorption capacity of the O-Ti3C2 MXene cathode for SO42− and the redox reaction of Zn/Zn2+ in the Zn/CNT anode, MZSCs have an extremely low self-discharge rate (1.92 mV h−1). This research is expected to provide a promising direction for next-generation, high-performance, anti-self-discharge and degradable devices.

Diminishing Self-Discharge of High-Loading Li-S Batteries with Oxygen-Rich Biomass Carbon Interlayers.

Lithium-sulfur batteries (Li-S) have possessed gratifying development in the past decade due to their high theoretical energy density. However, the severe polysulfide shuttling provokes undesirable self-discharge effect, leading to low energy efficiency in Li-S batteries. Herein, an interlayer composed of oxygen-rich carbon nanosheets (OCN) derived from bagasse is elaborated to suppress the shuttle effect and reduce the resultant self-discharge effect. The OCN interlayer is able to physically block the shuttling behavior of polysulfides and its oxygen-rich functional groups can strongly interact with polysulfides via O-S bonds to chemically immobilize mobile polysulfides. The self-discharge test for seven days further shows that the self-discahrge rate is diminished by impressive 93 %. As a result, Li-S batteries with the OCN interlayer achieve an ultrahigh discharge specific capacity of 710 mAh g-1 at a high mass loading of 7.18 mg. The work provides a facile method for designing functional interlayers and opens a new avenue for realizing Li-S batteries with high energy efficiency.

Study on Glyphosate Adsorption onto ZIF-8 Modified with Fe<sub>3</sub>O<sub>4</sub> Nanoparticles

Glyphosate (GLYPi) is an organophosphorus herbicide that behaves as an anionic substance in the aqueous phase. Even though it is stated as safe and non-toxic, the widespread use of GLYPi has raised environmental issues that need attention. This work used the positively charged metal-organic framework (MOF) of ZIF-8 to remove GLYPi via adsorption. Fe3O4 particles were hybridized with ZIF-8 to obtain Fe3O4@ZIF-8 via an in-situ deposition strategy to enhance the adsorption capacity toward GLYPi. The composite material (Fe3O4@ZIF-8) was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction, revealing rhombic dodecahedron-shaped particles and oxygen-rich functional groups. The adsorption results show that there is a synergistic effect of adding Fe3O4 to ZIF-8 in increasing the rate and capacity of adsorption on GLYPi, that is 0.0012 g/mg·min (Pseudo-second-order) and 73.57 mg/g (Langmuir), respectively, on pH 7 and 50 °C. GLYPi adsorption by Fe3O4@ZIF-8 was not influenced by coexisting anions (e.g., Cl-, NO3-, SO42-, and HCO3-). The reusability study showed that the adsorption efficiency of GLYPi by Fe3O4@ZIF-8 decreased significantly after the first cycle, which should be considered a future challenge for further studies. The adsorption mechanisms of GLYPi by Fe3O4@ZIF-8 involve electrostatic interaction and pore-filling. The results indicate that Fe3O4@ZIF-8 is a promising candidate for removing organophosphate compounds, which could be an excellent strategy for environmental protection.

Boosting acetaminophen degradation in water by peracetic acid activation: A novel approach using chestnut shell-derived biochar at varied pyrolysis temperatures

In this study, biochar derived from chestnut shells was synthesized through pyrolysis at varying temperatures from 300 °C to 900 °C. The study unveiled that the pyrolysis temperature is pivotal in defining the physical and chemical attributes of biochar, notably its adsorption capabilities and its role in activating peracetic acid (PAA) for the efficient removal of acetaminophen (APAP) from aquatic environments. Notably, the biochar processed at 900 °C, referred to as CN900, demonstrated an exceptional adsorption efficiency of 55.8 mg g−1, significantly outperforming its counterparts produced at lower temperatures (CN300, CN500, and CN700). This enhanced performance of CN900 is attributed to its increased surface area, improved micro-porosity, and a greater abundance of oxygen-containing functional groups, which are a consequence of the elevated pyrolysis temperature. These oxygen-rich functional groups, such as carbonyls, play a crucial role in facilitating the decomposition of the O–O bond in PAA, leading to the generation of reactive oxygen species (ROS) through electron transfer mechanisms. This investigation contributes to the development of sustainable and cost-effective materials for water purification, underscoring the potential of chestnut shell-derived biochar as an efficient adsorbent and catalyst for PAA activation, thereby offering a viable solution for environmental cleanup efforts.

Tetracycline (TC) removal from wastewater with activated carbon (AC) obtained from waste grape marc: activated carbon characterization and adsorption mechanism

In this study, activated carbons were obtained from grape marc for tetracycline removal from wastewater. Activated carbons were obtained by subjecting them to pyrolysis at 300, 500, and 700 °C, respectively, and the effect of pyrolysis temperature on activated carbons was investigated. The physicochemical and surface properties of the activated carbons were evaluated by SEM, FTIR, XRD, elemental analysis, N2 adsorption/desorption isothermal, thermal gravimetric (TG) and derivative thermogravimetric (DTG), and BET surface area analysis. When the BET surface areas were examined, it was found that 4.25 m2/g for activated carbon was produced at 300 °C, 44.23 m2/g for activated carbon obtained at 500 °C and 44.23 m2/g at 700 °C, which showed that the BET surface areas increased with increasing pyrolysis temperatures. The pore volumes of the synthesized activated carbons were 0.0037 cm3/g, 0.023 cm3/g, and 0.305 cm3/g for pyrolysis temperatures of 300, 500, and 700 °C, respectively, while the average pore size was found to be 8.02 nm, 9.45 nm, and 10.29 nm, respectively. A better adsorption capacity was observed due to the decrease in oxygen-rich functional groups with increasing pyrolysis temperature. It was observed that the activated carbon obtained from grape skins can easily treat hazardous wastewater containing tetracycline due to its high carbon content and surface functional groups. It was also shown that the activated carbon synthesized in this study has a higher pore volume despite its low surface area compared to the studies in the literature. Thanks to the high pore volume and surface active groups, a successful tetracycline removal was achieved.Graphical

Correlated IR-SEM-TEM studies of three different grains from Ryugu: From the initial material to post-accretional processes

In order to better constrain the alteration history of the Ryugu parent body, we performed a multi-analytical study combining scanning electron microscopy, transmission electron microscopy and infrared spectroscopy on sections extracted from the three fragments A0064-FO019, A0064-FO021 and C0002-FO019 returned from Ryugu by the Hayabusa2 space mission. The three sections show large differences in terms of structure, mineralogy and infrared signature. Section A0064-FO019 resembles the major Ryugu lithology with the presence of both fine-grained phyllosilicates (fg-phyllos) with embedded nanosulfides and coarse-grained phyllosilicates (cg-phyllos), whereas section C0002-FO019 belongs to the group of the less altered lithologies with the presence of anhydrous minerals embedded in a partially amorphous matrix. Section A0064-FO021 also belongs to this group but shows two different lithologies, a compact amorphous one and a more porous and very fractured one showing the presence of Na-rich phosphate, calcite and olivine. The two less altered lithologies (sections A0064-FO021 and C0002-FO019) show the presence of numerous mineralogical features similar to those observed in cometary interplanetary dust particles, ultra-carbonaceous Antarctic micrometeorites or in the CM Paris meteorite, i.e. amorphous and partially crystallized matrix with GEMS-like ghosts objects, whisker olivine, phosphide, or FeNi metal. This supports an outer solar system origin common with that of cometary material for the Ryugu parent body. Combined with the results of Nakamura et al. (2022b) reporting the presence of a lithology showing the presence of GEMS-like objects, we propose that section C0002-FO019 represents the onset of aqueous alteration of such primitive materials. The cg-phyllos and fg-phyllos of section A0064-FO019, i.e. of the major Ryugu lithology, representing the advanced stage of alteration, exhibit distinctive IR signatures with a higher abundance of oxygen-rich functional groups in the organic matter (OM) from the cg-phyllos. We thus suggest the following chronology of formation and evolution for Ryugu: (1) accretion of highly porous aggregate of GEMS-like units with fine-grained high-temperature anhydrous silicates, (2) onset of alteration with the dissolution of primary nanosulfides and development of amorphous/partially crystallized material in the pores, (3) crystallization of fg-phyllos with a second generation of sulfides, (4) later formation of cg-phyllos devoid of nanosulfides and their associated oxygen-rich OM in a more water-rich environment.

How does adsorptive fractionation of dissolved black carbon on ferrihydrite affect its copper binding behaviors? A molecular-scale investigation

Adsorptive fractionation of dissolved black carbon (DBC) on minerals is proven to alter its molecular composition, which will inevitably affect the environment fate of heavy metals. However, the effects of molecular fractionation on the interaction between DBC and heavy metals remain unclear. Herein, we observed that the selective adsorption of ferrihydrite caused molecular changes of DBC from high molecular weight/unsaturation/aromaticity to low molecular weight/saturation/aliphatics. This process accompanied by a retention of carbohydrate and a reduction of oxygen-rich functional groups (e.g., polyphenols and carboxyl) and long carbon chain in DBC. The residual DBC in aqueous phase demonstrated a weaker binding affinity to copper compared to the original DBC. This decrease in binding affinity was primarily attributed to the adsorption of polycyclic condensed aromatic compounds of 200–250 Da, oxygen-rich polycyclic condensed aromatic compounds of 250–300 Da, oxygen-rich non-polycyclic aromatic compounds of 300–450 Da, and non-polycyclic aromatic compounds of 450–700 Da in DBC by ferrihydrite. Additionally, the retention of carbohydrates and aliphatic compounds of 300–450 Da also made a significant contribution. Notably, carboxylic groups rather than phenolic groups were the dominant oxygen-containing functional groups responsible for this affinity reduction. This study has significant implications for understanding of the biogeochemical processes of DBC at soil-water interface and surface water, especially its role in the transportation of heavy metals.

Role of oxygen functional groups and attachment of Au nanoparticles on graphene oxide sheets for improved photodetection performance.

Integrating low-dimensional graphene oxide (GO) with conventional Si technology offers innovative strategies for developing ultrafast wideband photodetectors. In this study, we synthesized GO and explored its potential application in broadband photodetection alongside silicon heterostructures. The as-synthesized GO contains various oxygen functional groups, as evidenced by X-ray photoelectron and Fourier transform infrared spectroscopy. These functional groups contribute to increased photo absorption, enhancing photodetection performance. The systematic reduction of these functional groups from the GO surface via thermal annealing decreases photo absorption and consequently lowers the photocurrent. This reduction diminishes photo absorption and amplifies the dark current by approximately 25 times, from 20 nA to 496 nA. This dark current increase is attributed to the electron mobility following the reduction of functional groups. However, attaching plasmonic gold nanoparticles (Au NPs) to the GO surface enhances UV-Vis absorption in the visible region, enabling broadband detection. The even distribution of attached Au NPs on the GO surface is confirmed through field emission transmission electron microscopy. While thermal annealing of GO diminishes the responsivity from 4.6 A W-1 to 3.0 A W-1, the attachment of Au NPs augments the responsivity by more than two-fold, reaching 10.0 A W-1. Thus, it highlights the importance of rich oxygen functional groups in GO and the attachment of Au NPs to achieve more efficient photo-sensing properties.

Carbon Microspheres with Cr(VI) Adsorption Performance were Prepared by In-situ Hydrothermal Carbonization Method

Biochar material is a renewable adsorbent widely used for treating contaminated wastewater. The hydrothermal carbon (HTC) were prepared from low polymeric sugars and low concentration glucose under hydrothermal carbonization reactions without using dispersants. The composition and structure of the biochar produced were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy (Raman), and N2 adsorption-desorption, indicating that amorphous graphitic carbon was obtained. Experimental results from the static adsorption of Cr(VI)-contaminated wastewater showed that HTCP-2 exhibited the highest adsorption capacity for Cr(VI), with a maximum adsorption capacity of 22.62 mg.g−1.The adsorption Cr(VI), MB, and RhB by the synthesized biochar all conformed to the pseudo-second-order kinetic model and Freundlich isotherm, suggesting a multilayer chemical adsorption process. Additionally, the synthesized HTC surface is enriched with a significant amount of oxygen-rich functional groups, which also has good adsorption performance for cationic dyes. Furthermore, the test results of fluorescence, photocurrent, and impedance indicate that HTCP-2 possesses the ability to generate and separate photoinduced charge carriers. This implied that HTCP-2 can be used for the preparation of adsorption photocatalysts, which effectively remove environmental pollutants through the synergistic effect of adsorption-photocatalysis. This study provides a research foundation for advancing water treatment technologies. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Crystalline-amorphous Co/Co3O4 derived from a low-temperature etching of ZIF-67 for oxygen-invovled catalytic reactions

Development of a simple method for synthesizing transition metal-based bifunctional catalysts is of great importance in the context of oxygen-involved electrochemical energy conversion and storage devices. In this effort, electrochemical catalysts consisting of amorphous cobalt and cobalt oxides on graphene oxide (GO) were fabricated using a solvothermal process followed by etching ZIF-67 with oxygen-rich functional groups on GO (≈ 29 at. %) in a weak reduction atmosphere at 400 ℃. During the calcination process forming the ZIF-67@GO-based materials, exposed cobalt metal centers are created by partial vaporization and oxidation of ZIF-67. Also, metal ions are reduced to form Co and partially combine with oxygen from GO to generate amorphous Co3O4. Moreover, the porous framework structure of ZIF is retained under the mild calcination temperatures used. Benefiting from their porous framework and heteroatoms-doped composition, the ZIF-67@GO-based materials have low overpotentials of 319 mV at 10 mA cm−2 and high catalytic activities toward the oxygen evolution and oxygen reduction reactions in an alkaline electrolyte. In addition, the liquid zinc-air battery assembled with the ZIF-67@GO composite produced at a calcination temperature of 400 ℃ displays a high performance. Overall, the results demonstrate that the ZIF-67@GO composites have the potential to be high-performing catalysts in energy conversion devices. The readily controllable and high-yielding calcination method in this study is expected to serve as a model for new strategies to synthesize low-cost and efficient bifunctional electrocatalysts.