Role Of Oxygen Functional Groups Research Articles

Enhancing electrochemical energy storage in Zinc hybrid capacitors using 3D-printed GO/AC electrodes with Oxygen functional groups

Zinc-ion hybrid capacitors (ZIHCs), promising for energy storage, encounter challenges such as mismatched positive and negative electrode capacities. Addressing this, increasing the thickness of positive electrode proves effective. However, traditional thick electrodes show an extended ion diffusion paths, which slows reactions and decreasing charge-discharge efficiency. Innovations in electrode structures have been achieved through 3D printing technology with an "embedded" composite material of activated carbon and graphene oxide, creating grids with varying layers to explore the relationship between layer number and capacitor performance. Density Functional Theory (DFT) simulations confirm the crucial role of oxygen functional groups on graphene oxide in enhancing storage capacity, with these findings supported by excellent electrochemical performance in tests. Precise control of electrode structures through 3D printing optimizes ion transport pathways, achieving a high specific capacity of 0.92 mAh cm−2 at a current density of 10 mA cm−2, maintaining 86.4 % cycle stability after 8,000 cycles. These results underscore the potential of 3 D printing to advance electrode design and suggest new directions for research.

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.

Unveiling the role of oxygen doping in activated carbon cathode for potassium-ion capacitors

Heteroatom-doped activated carbon that induces pseudocapacitive anion storage is a promising high-capacity cathode compatible with advanced anodes for potassium-ion capacitors (PICs). However, the mechanism of heteroatom-related anion storage in potassium-based electrolyte has rarely been explored and is not well understood. Herein, activated carbon fibers with oxygen doping (ACNFs-O) is conducted to explore the role of oxygen functional groups on the anion storage performance. The ACNFs-O cathode shows a high reversible capacity of 88.4 mAh g−1 at 0.1 A g−1 with a high-rate performance of 57.3 mA h g−1 at 6.0 A g−1, and a long-term stability, which is much higher than that of the non-oxygen-doped sample (ACNFs-H). The experimental characterizations and theoretical calculations reveal that the redox-active carbonyl (CO) group tunes the electrochemical properties of the carbon to provide a pseudocapacitive contribution for improved anion storage. As expected, the PICs with the ACNFs-O as the cathode materials exhibit a high energy density and power density (125.4 Wh kg−1 at 193 W kg−1), which performs 50% better than that of ACNFs-H. This work could provide insight into the design of low-cost and sustainable cathodes and an understanding of the anion storage mechanism of heteroatom-doped carbons for PICs.

Density Functional Theory Calculations of the Effect of Oxygenated Functionals on Activated Carbon towards Cresol Adsorption

The mechanism of adsorption of p-cresol over activated carbon adsorbent and the specific role of oxygen functional groups on cresol adsorption were studied using density functional theory (DFT) calculations. All the energy calculations and geometry optimization pertaining to DFT calculations were done using the B3LYP hybrid functional at basis set 6-31g level of theory in a dielectric medium of ε = 80 (corresponding to water). The interaction of cresol with different activated carbon models, namely pristine activated carbon, hydroxyl functionalized activated carbon, carbonyl functionalized activated carbon, and carboxyl functionalized activated carbon, were considered, and their adsorption energies corresponded to −416.47 kJ/mol, −54.73 kJ/mol, −49.99 kJ/mol, and −63.62 kJ/mol, respectively. The high adsorption energies suggested the chemisorptive nature of the cresol-activated carbon adsorption process. Among the oxygen functional groups, the carboxyl group tended to influence the adsorption process more than the hydroxyl and carbonyl groups, attributing to the formation of two types of hydrogen bonds between the carboxyl activated carbon and the cresol simultaneously. The outcomes of this study may provide valuable insights for future directions to design activated carbon with improved performance towards cresol adsorption.

Enhanced catalytic performance of the carbon-supported Ru ammonia synthesis catalyst by an introduction of oxygen functional groups via gas-phase oxidation

Carbon-supported ruthenium catalysts are very promising application in ammonia synthesis. Here we show that the oxygen functional groups can be introduced into carbon preloaded with Ru species by HNO3 gas-phase oxidation treatment. The results reveal that the presence of oxygen functional groups facilitates the desorption of hydrogen species. Moreover, the decomposition of barium nitrate is accelerated, and the ill effects of carbon methanation and hydrogen poisoning are effectively alleviated. The combination of the change in the existing form of Ba promoter, the acceleration in the desorption and exchange of hydrogen species accounts for the superior ammonia synthesis activity of Ru catalyst with HNO3 gas-phase treatment. Understanding the role of oxygen functional groups provides design rules for the rational design of carbon-supported Ru catalyst with highly activity and stability for ammonia synthesis or other hydrogen-involved reactions.

Elucidating the roles of oxygen functional groups and defect density of electrochemically exfoliated GO on the kinetic parameters towards furazolidone detection.

Using electrochemically exfoliated graphene oxide (GO)-modified screen-printed carbon electrodes for the detection of furazolidone (FZD), a nitrofuran antibiotic, was explored. In this study, we designed some GO samples possessing different oxygen functional group content/defect density by using ultrasonic irradiation or microwave techniques as supporting tools. The difference in physical characteristics of GO led to the remarkable change in kinetic parameters (electron transfer rate constant (k s) and transfer coefficient (α)) of electron transfer reactions at K 3/K 4 probes as well as the FZD analyte. Obtained results reveal that the GO-ultrasonic sample showed the highest electrochemical response toward FZD detection owing to the increase in defect density and number of edges in the GO nanosheets under ultrasonic irradiation. The proposed electrochemical nanosensor enabled the monitoring of FZD in the linear range from 1 μM to 100 μM with an electrochemical sensitivity of 1.03 μA μM-1 cm-2. Tuning suitable electronic structures of GO suggests the potentiality of advanced GO-based electrochemical nanosensor development in food-producing animal safety monitoring applications.

2021: A Surface Odyssey. Role of Oxygen Functional Groups on Activated Carbon-Based Electrodes in Vanadium Flow Batteries.

The market breakthrough of vanadium flow batteries is hampered by their low power density, which depends heavily on the catalytic activity of the graphite‐based electrodes used. Researchers try to increase their performance by thermal, chemical, or electrochemical treatments but find no common activity descriptors. No consistent results exist for the so‐called oxygen functional groups, which seem to catalyze mainly the VIII/VII but rarely the VVO2 +/VIVO2+ redox reaction. Some studies suggest that the activity is related to graphitic lattice defects which often contain oxygen and are therefore held responsible for inconsistent conclusions. Activation of electrodes does not change one property at a time, but rather surface chemistry and microstructure simultaneously, and the choice of starting material is crucial for subsequent observations. In this contribution, the literature on the catalytic and physicochemical properties of activated carbon‐based electrodes is analyzed and evaluated. In addition, an outlook on possible future investigations is given to avoid the propagation of contradictions.

Role of oxygen functional groups in Pb2+ adsorption from aqueous solution on carbonaceous surface: A density functional theory study

The adsorption mechanism of Pb2+ from aqueous solution on carbonaceous surface modified with oxygen functional groups was investigated by using density functional theory method. The zigzag model with seven benzene rings and armchair model with four benzene rings were used to simulate the different structures of carbonaceous surfaces. It was found that the adsorption of Pb2+ on the pure zigzag surface was chemisorption with the adsorption energy of − 306.26 to − 322.36 kJ/mol, while that on the armchair surface was physisorption with the adsorption energy of − 32.39 kJ/mol. The introduction of oxygen functional groups significantly enhanced the Pb2+ adsorption on the armchair surface. The physisorption changed to chemisorption after adding carboxyl, phenolic hydroxyl, or carbonyl functional group, indicating the stronger adsorption ability of the carbonaceous surfaces after modification. On the zigzag surface, however, the studied functional groups cannot benefit the Pb2+ adsorption. The results showed that the Pb2+ tended to adsorb on the carbon atoms instead of moving to the oxygen atoms from the introduced functional groups for adsorption, which suggests that the oxygen functional groups promoted the Pb2+ adsorption by increasing the activity of their neighboring carbon atoms.

Unveiling the Synergistic Role of Oxygen Functional Groups in the Graphene-Mediated Oxidation of Glutathione.

This is the first report of an atomic-scale direct oxidation mechanism of the thiol group in glutathione (GSH) by epoxides on graphene oxide (GO) at room temperature. The proposed reaction mechanism is determined using a coupled experimental and computational approach; active sites for the reaction are determined through examination of GO surface chemistry changes before and after exposure to GSH, and density functional theory (DFT) calculations determine the reaction barriers for the possible GO-GSH reaction schemes. The findings build on the previously established catalytic mechanism of GSH oxidation by graphenic nanocarbon surfaces and importantly identify the direct reaction mechanism which becomes important in low-oxygen environments. Experimental results suggest epoxides as the active sites for the reaction with GSH, which we confirm using DFT calculations of reaction barriers and further identify a synergism between the adjacent epoxide and hydroxyl groups on the GO surface. The direct oxidation mechanism at specific oxygen sites offers insight into controlling GO chemical reactivity through surface chemistry manipulations. This insight is critical for furthering our understanding of GO oxidative stress pathways in cytotoxicity as well as for providing rational material design for GO applications that can leverage this reaction.

Changes in characteristics of Pt-functionalized RGO nanocomposites by electron beam irradiation for room temperature NO2 sensing

In this study, reduced graphene oxide (RGO) nanosheets were synthesized and then functionalized with Pt nanoparticles (NPs) for gas sensing studies at room temperature. Pt-functionalized RGOs (Pt-RGOs) were irradiated by a 2 MeV electron beam with different doses of 100 and 500 kGy (Pt-RGO-100 and Pt-RGO-500) to study the role of electron beam irradiation (EBI) on properties and NO2 gas sensing characteristics. Different characterization techniques verified the generation of structural defects after EBI. Additionally, NO2 sensing tests at room temperature revealed that the Pt-RGO-100 sensor had the highest response to NO2 gas as well as the shortest response time. We surmise that the improved sensing signal with respect to NO2 gas for Pt-RGO-100 sensor was related to the role of oxygen functional groups. However, decreases in the response for Pt-RGO-500 sensor were related to the creation of reactive oxygen gases that could be adsorbed on the active defects of the RGO by the interaction of electron beams with oxygen species in the ambient air, leading to a decrease of the effective defect sites and decreases of the sensing response. This work suggests progress towards an improved performance of RGO-based gas sensors that can work at low temperature, by using EBI as a clean tool applied at room temperature with Pt-functionalization.

High-performance Li-ion batteries based on graphene quantum dot wrapped carbon nanotube hybrid anodes

Since Akira Yoshino first proposed the usage of the carbonaceous materials as an anode of lithium ion batteries (LIBs) in 1985, carbonaceous materials such as graphite and graphene have been widely considered as LIB anodes. Here, we explored the application of novel carbonaceous LIB anodes incorporating graphene quantum dots (GQDs). We fabricated a freestanding all-carbon electrode based on a porous carbon nanotube (CNT) sponge via a facile in-situ hydrothermal deposition technique, creating coaxial structure of GQD-coated CNTs (GQD@CNTs) through electrostatic interaction and π-π stacking with tunable loading and functionalization. This hybrid structure combined conductive CNTs with highly active GQDs, in which GQDs with predesigned functional groups provided massive storage sites for Li ions and the 3D CNT frameworks avoided the agglomeration of GQDs, together contributing to a high specific capacity (700 mAh}g−1 at 100 mA}g−1 after 100 cycles) and rate performance. Even at a high current density of 1,000 mA}g−1, the reversible specific capacity remained at 483 mAh}g−1 after 350 cycles. In particular, the mechanism study demonstrated the important role of oxygen functional groups of GQDs in promoting the performance of the LIB anodes by controlled grafting of GQDs onto various porous-carbon and metal-foam based structures.

Cover Feature: Roles of Oxygen Functional Groups in Carbon Nanotubes‐Supported Ag Catalysts for Electrochemical Conversion of CO2 to CO (ChemElectroChem 8/2020)

Cover Feature: Roles of Oxygen Functional Groups in Carbon Nanotubes‐Supported Ag Catalysts for Electrochemical Conversion of CO₂ to CO (ChemElectroChem 8/2020)

Roles of Oxygen Functional Groups in Carbon Nanotubes‐Supported Ag Catalysts for Electrochemical Conversion of CO2 to CO

AbstractCarbon nanotubes (CNTs)‐supported metal‐based catalysts applied in the electrochemical reduction of CO2 (CO2ER) have attracted extensive research recently. Nevertheless, insight into the roles of surface oxygen functional groups in these catalysts on CO2ER is still deficient. Herein, three catalysts were reasonably fabricated by chemically loading Ag nanoparticles (NPs) on the oxygenic CNTs (CNT−COOH, CNT−OH and CNT−CO) with precise tuning oxygen functional groups, and then used to explore the effect of oxygen functional groups on the electrocatalytic performance of Ag NPs for CO2ER. Compared with the other two counterparts, Ag/CNT−COOH with the highest content of carboxyl groups possesses the most uniform size and dispersion of Ag NPs and the strongest surface acidic environment, which enable it to exhibit the highest current density and Faradaic efficiency for CO production at high overpotential region (E≤−1.0 V vs. RHE). This work broadens the understanding of surface oxygen functional groups of catalysts in enhancing CO2ER performance, and provides guidance for the design and synthesis of high‐performance catalysts.

Insights into the Electron-Transfer Regime of Peroxydisulfate Activation on Carbon Nanotubes: The Role of Oxygen Functional Groups.

Carbon-driven advanced oxidation processes are appealing in wastewater purification because of the metal-free feature of the carbocatalysts. However, the regime of the emerging nonradical pathway is ambiguous because of the intricate carbon structure. To this end, this study was dedicated to unveil the intrinsic structure-performance relationship of peroxydisulfate (PDS) activation by carbon nanotubes (CNTs) toward nonradical oxidation of organics such as phenol (PE) via electron transfer. Eighteen analogical CNTs were synthesized and functionalized with different categories and contents of oxygen species. The quenching tests and chronopotentiometry suggest that an improved reactivity of surface-regulated CNTs was attributed to the reinforced electron-transfer regime without generation of free radicals and singlet oxygen. The quantitative structure-activity relationships were established and correlated to the Tafel equation, which unveils the nature of the nonradical oxidation by CNT-activated PDS complexes (CNT-PDS*). First, a decline in the concentration of oxygen groups in CNTs will make the zeta potential of the CNT become less negative in neutral solutions, which facilitated the adsorption of PDS because of weaker electrostatic repulsion. Then, the metastable CNT-PDS* was formed, which elevated the oxidation capacity of the CNT. Finally, PE would be oxidized over CNT-PDS* via electron transfer to fulfill the redox cycle. Moreover, the nonradical oxidation rate was uncovered to be exponentially related with the potential of the complexes, suggesting that the nonradical oxidation by the CNT-PDS* undergoes a mechanism analogous to anodic oxidation.

Mass Transfer and Reaction Kinetic Enhanced Electrode for High‐Performance Aqueous Flow Batteries

AbstractA scalable and efficient process to modify electrodes with enhanced mass transfer and reaction kinetics is critical for redox flow batteries (RFBs). For the first time, this work introduces electrochemical exfoliation as a surface modification method of graphite felt (GF) to enhance the mass transfer and reaction kinetics in RFBs. Anion intercalation and subsequent gas evolutions at room temperature for one minute expand the graphite layers that increase the electrode surface area. Meanwhile, sufficient oxygen functional groups are introduced to the electrode, resulting in enhanced reaction kinetics and improved hydrophilicity. Further, spin‐polarized density functional theory is employed to reveal the role of oxygen functional groups in accelerating the vanadium redox reaction. Benefitting from sufficient oxygen groups, larger surface area, and superior wettability, the as‐prepared exfoliated GF (E‐GF) shows exceptional electrocatalytic activity with minimized overpotential, higher volumetric capacity, and improved energy efficiency. The redox flow battery assembled with the E‐GF electrode delivers voltage and energy efficiencies of 89.72% and 86.41% at the current density of 100 mA cm−2, respectively. Remarkably, compared to the traditional GF treatment method, the elimination of the high temperature and long‐time treatment processes make this approach much more energy and time efficient, scalable, and affordable for large‐scale manufacturing.

Roles of Oxygen Functional Groups in Hydrogen Sulfide Adsorption on Activated Carbon Surface: A Density Functional Study

The hydrogen sulfide (H2S) removal ability of activated carbon is closely related to surface oxygen groups, yet the roles of oxygen groups in the process of H2S adsorption on activated carbon have ...

Role of oxygen functional groups for improved performance of graphene-silicone composites as a thermal interface material

We report the findings of our experimental investigation on the performance of reduced graphene oxide (rGO)/silicone composite as a thermal interface material (TIM) influenced by the loading factor, surface functionality, and structural properties of graphene. The experimental data reveals that in addition to the loading factor, the thermal conductance of TIMs is greatly impacted by the density of oxygen-functionality (phenolic group) in rGO, and the morphological and structural properties introduced during the thermal reduction (deoxygenation) of graphene oxide to rGO. In particular, the phenolic groups prominently formed on the basal plane of rGO play a significant role in decreasing the interfacial thermal resistance. The results also show that the larger sp2 graphitic structures and the morphological properties of rGO increase the degree of dispersion in the matrix. A dynamic interplay between these factors determines the final value of the thermal conductance observed for different composites. An optimum combination of these factors led to the maximum thermal conductance (541 W/m2K) for the T-rGO600 (thermally-reduced graphene oxide processed at 600 °C)/silicone composite. The proposed underlying physics backed by the experimental data should be useful in designing high thermal performance TIMs with carbonaceous nanomaterials, including carbon nanotubes, graphene nanoplatelets, and carbon blacks acting as additives.

High Electrochemical Performance from Oxygen Functional Groups Containing Porous Activated Carbon Electrode of Supercapacitors.

Carbon electrode materials for double layer capacitors have attracted much attention, due to their low cost and abundant sources. Their low specific capacitance, however, hinders the development of carbon electrode materials. In this paper, the large specific surface area commercial activated carbons, rich in micropores, were initially oxygen-functionalized by treatment using concentrated H2SO4, saturated (NH4)2S2O8, and H2SO4/(NH4)2S2O4 mixed oxidants, respectively. The as-prepared samples were analyzed using N2 adsorption/desorption isotherms, X-ray photoelectron spectroscopy, and Boehm titration, and used as electrode materials for supercapacitors. Characterization results displayed that the oxidation treatment decreased the specific surface area along with increasing oxygen content. The electrode test showed that the electrochemical activity increased as oxygen content increased. The result that oxygen-functionalized activated carbon, even with a lower specific surface area but much more oxygen content, had higher capacity than pristine activated carbon, tells of the critical role of oxygen functional groups. The excellent capacitive performance suggests a good potential for oxygen functional carbon material to be a highly promising electrode material for supercapacitors.

Insights into the role of oxygen functional groups and defects in the rechargeable nonaqueous Li–O2 batteries

Since electrode surfaces primarily house the sites of oxygen reduction/evolution reactions, surface chemistry is pivotal for both charge and discharge processes of Li–O2 batteries. Herein, we introduce oxygen-containing functional groups associated with defects on the carbon fiber papers (functionalization) via acid treatment and investigate their effects on the rechargeable nonaqueous Li–O2 batteries. The discharge platform increases from 2.68 V to 2.79 V, meanwhile the decreased charge overpotential (a drop of 0.84 V) is also observed after functionalization. It is found that the discharge products formed on pristine carbon fiber exhibit a huge toroidal-like structure, in contrast to the porous flake clusters with much smaller size on the functionalized carbon fiber. On the other hand, the smaller product clusters are found to be much easier to be oxidized, leading to remarkably reduced charge overpotential. In this regard, the decomposition of electrolyte and corrosion of carbon cathode are dramatically alleviated, thus leading to greatly promoted cycling performance. All the experimental facts suggest that the oxygen functional groups associated with defects could provide tremendous active sites for the nucleation of discharge products and result in remarkably decreased overpotential for both the oxygen reduction and the oxygen evolution reaction in our cases.

Crucial role for oxygen functional groups in the oxygen reduction reaction electrocatalytic activity of nitrogen-doped carbons

Generally, a significant amount of oxygen functional groups (OFGs) usually exist on the surface of nitrogen-doped carbons. Unfortunately, the role of OFGs on the oxygen reduction reaction (ORR) electrocatalytic activity of nitrogen-doped carbons is rarely discussed. Herein, we report that the OFGs play a crucial role on the ORR electrocatalytic activity of nitrogen-doped carbons. A nitrogen doped carbon foam (NCF) containing OFGs was prepared by pyrolysis of melamine foam. The species of the OFGs were then tuned by chemical reduction, and their effects on the ORR electrocatalytic activity of the NCF were investigated by electrochemical measurements, X-ray photoelectron spectroscopy and solid-state NMR spectroscopy. Results showed that the ORR electrocatalytic activity of the NCF greatly decreased after chemical reduction. The OFGs in the form of quinone were found to be crucial for the ORR electrocatalytic activity of the NCF. This study not only provided a new and effective strategy for investigating the effect of OFGs on the ORR electrocatalytic activity of nitrogen-doped carbons, but also presented a new insight into understanding their electrocatalytic mechanism.