Ordered Mesoporous Carbon Electrode Research Articles

Wettability-modulated ordered mesoporous carbon electrodes for electrocatalytic reactions involving gases

Herein, a series of ordered mesoporous carbon (OMC) electrodes with switchable surface wettability were developed. These electrodes are favorable for water electrolysis at high current densities and increase the production of H2O2 in the oxygen reduction reaction. The hydrophilic OMC electrodes can promote the oxygen evolution reaction performance by separating O2 bubbles promptly. The hydrophobic OMC electrodes provide a directional diffusion channel for O2 transport to improve the efficiency of O2 utilization. The hydrophobic OMC electrode is used for green synthesis of H2O2 with a production rate of 48.1 mmol gcat−1 h−1, Faraday efficiency of 86.3%, and minimum energy consumption of 3.07 kWh kg−1. The constructed electro-Fenton system reached 87% and 73% removal rate of rhodamine B and methyl orange within 60 min, respectively. The hydrophilic/hydrophobic electrodes are expected to have an important function in electrocatalytic reactions involving gases.

Earth-abundant metal-free carbon-based electrocatalysts for Zn-air batteries to power electrochemical generation of H2O2 for in-situ wastewater treatment

The overuse of fossil fuel has caused a serious energy crisis and environmental pollution. In this study, we rationally devised an integrated system, in which novel earth-abundant metal-free carbon-based electrocatalysts were used to catalyze oxygen reduction reaction (ORR) in Zn-air batteries for renewable energy storage as a power source for electrochemical generation of H2O2 as an oxidant for in-situ degradation of pollutants in wastewater. It was noted that the newly-developed ordered mesoporous carbon (OMC) and N-doped OMC (NOMC) exhibited high selectivity for 2e− ORR to produce H2O2 and high selectivity for 4e− ORR at the cathode of Zn-air batteries, respectively. The OMC electrode showed a H2O2 yield as high as 366.9 mg/L in 2 h at 0.5 V, leading to a high current efficiency ~73.6%, The subsequent use of thus-produced H2O2 for Rhodamine B (RhB) candidate pollutant degradation exhibited an 90% removal efficiency in 2 h, showing a great promise for practical wastewater treatment. This work represents a breakthrough in the development of a new concept and novel integrated systems to address the current energy and environmental changes.

Synthesis of Ordered Mesoporous Carbon from Vietnam Natural Kaolin Clay for Supercapacitor Application

In nature, kaolin clay is referred to a readily available cheap source of silicon and used in various fields such as the paper, ceramic, paint, plastic, rubber, and cracking catalyst industries. This paper introduces utilization of natural kaolin clay for a new application. In particular, the kaolin clay is used as a new raw material for synthesis of ordered mesoporous carbon (OMC) materials, which serve as electrode active materials for supercapacitors. Kaoline used in the present work is originated from Yen Bai province (Vietnam). After subjected several steps of the treatment process, silica present in the kaolin clay is converted to sodium silicate and used directly as a source of silicon for the synthesis process of mesoporous porous silica (SBA-15). The synthesized SBA-15 mesoporous silicas exhibit rod-like nanostructure with the specific area of 432.7 m2 g-1 and the mean pore size of 7-8 nm. Subsequently, SBA-15 silica serves as hard template for preparation of OMCs by using nanocasting method. The OMCs carbonized at different temperatures in the absence and presence of boric acid reveal highly ordered mesoporous structure with the highest specific area of 1039.2 m2 g-1 and the mean pore size ranging from 6 to 7 nm. As used as electrode active material in 6 M KOH aqueous solution, the resultant OMCs exhibit excellent capacitive performance with a specific capacitance higher than 80 F g-1 at a scan rate of 5 mV s-1. The obtained results show that, in addition to the high specific area, the electrical conductivity also plays an important role in enhancing energy storage ability of the OMC electrodes. At the same carbonization temperature, the high surface area plays crucial role. However, at the higher carbonization temperatures, effect of the electrical conductivity of the materials prevails over the high surface area. This study illustrates highly application feasibility of Vietnam natural kaolin clay as available and cheap raw material source for synthesis of electrode active materials with the high supercapacitive performance for electrochemical double layer capacitors.

Synthesis of Polyaniline-Coated Ordered Mesoporous Carbon Composite Electrode Material for Supercapacitor and Its Enhanced Electrochemical Performance.

The polyaniline-coated ordered mesoporous carbon (PCOMC) material was prepared by chemical polymerization of aniline monomers on the ordered mesoporous carbon (OMC). The synthesized PCOMC materials were characterized by scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption isotherms and Fourier infrared spectroscopy. It was demonstrated that the polyaniline was successfully incorporated and well deposited on the external surface and inner pores of the OMC material. Furthermore, the electrochemical performance of the original OMC and PCOMC materials are compared by using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. The results showed that the electrochemical performance of the OMC material was enhanced after the incorporation of polyaniline. The specific capacitance of PCOMC electrode (813.4 F/g) measured by cyclic voltammetry at the scan rate of 2 mV/s was much higher than that of the OMC electrode (200.9 F/g). The discharge specific capacitance of the PCOMC supercapacitor could be kept at 119.4 F/g when the current density was 5 A/g, indicating its good rate performance even at high charge/discharge current density. Moreover, the PCOMC supercapacitor exhibited long cycling stability with the capacitance retention remained 77% after 3500 cycles.

The Effect of Pore Size Controlled Carbon for Lithium Oxygen Batteries

The lithium-oxygen battery has been attracting great attention around the world due to its extremely high energy density (i.e., 1-2 kWh kg-1), which could well satisfy the ever increased energy requirement from electronic devices, especially the electric vehicle and plug-in hybrid electric vehicle.1-3 This exceptional energy potentiality has trigged the worldwide interest in this super energy storage system. However, despite large R&D efforts devoted to its implementation, several issues, associated with both electrodes and electrolytes, have so far limited the performance of the lithium oxygen battery due to few discharge-charge cycles and low rate capability.4, 5 Many materials are used for cathode in lithium oxygen battery. Among them, carbon is the mostly used material because of the advantage in the way that amount and cost, although it has been talked making by-product like Li2CO3. (Some paper told that not only carbon but also electrolyte makes the problem in lithium oxygen battery system)In this study, we show that Ordered mesoporous carbon (OMC) with highly ordered pore channels which was applied as an oxygen-side electrode for a lithium-oxygen battery.To evaluate the effect of the pore channel size on battery performance, OMCs possessing two different pore sizes (6 and 17 nm) were employed. When cycled at a current density of 200 mA g-1carbon, the OMC electrodes reduced polarization in the oxygen evolution reaction by 0.1 V compared to those consisting of conventional super P carbon electrode. X-ray diffraction and transmission electron microscopy of the discharged oxygen electrodes provided evidence for the formation of amorphous Li2O2, a product of the oxygen reduction reaction, inside the OMC pores rather than on the electrode surface as in the case of the super P electrode. The OMC electrodes were also effective at high current densities (500 mA g-1carbon and 1000 mA g-1carbon).

Highly Conductive Ordered Mesoporous Carbon Based Electrodes Decorated by 3D Graphene and 1D Silver Nanowire for Flexible Supercapacitor

Ordered mesoporous carbon (OMC) is considered one of the most promising materials for electric double layer capacitors (EDLC) given its low‐cost, high specific surface area, and easily accessed ordered pore channels. However, pristine OMC electrode suffers from poor electrical conductivity and mechanical flexibility, whose specific capacitance and cycling stability is unsatisfactory in flexible devices. In this work, OMC is coated on the surface of highly conductive three‐dimensional graphene foam, serving as both charge collector and flexible substrate. Upon further decoration with silver nanowires (Ag NWs), the novel architecture of Ag NWs/3D‐graphene foam/OMC (Ag‐GF‐OMC) exhibits exceptional electrical conductivity (up to 762 S cm−1) and mechanical robustness. The Ag‐GF‐OMC electrodes in flexible supercapacitors reach a specific capacitance as high as 213 F g−1, a value five‐fold higher than that of the pristine OMC electrode. Moreover, these flexible electrodes also exhibit excellent long‐term stability with >90% capacitance retention over 10 000 cycles, as well as high energy and power density (4.5 Wh kg−1 and 5040 W kg−1, respectively). This study provides a new procedure to enhance the device performance of OMC based supercapacitors, which is a promising candidate for the application of flexible energy storage devices.

Ordered Mesoporous Carbon Electrodes for Li–O2 Batteries

Ordered mesoporous carbon (OMC) with highly ordered pore channels was applied as an oxygen-side electrode for a Li-O2 battery. To evaluate the effect of the pore channel size on battery performance, we employed OMCs possessing two different pore sizes (6 and 17 nm). When cycled at a current density of 200 mA g(-1)carbon, the OMC electrodes reduced polarization in the oxygen evolution reaction by 0.1 V compared to those consisting of conventional super P carbon electrode. X-ray diffraction and transmission electron microscopy of the discharged oxygen electrodes provided evidence for the formation of amorphous Li2O2, a product of the oxygen reduction reaction, inside the OMC pores rather than on the electrode surface as in the case of the super P electrode. The OMC electrodes were also effective at high current densities (500 mA g(-1)carbon and 1000 mA g(-1)carbon).

Large surface area carbon material with ordered mesopores for highly selective determination of l-tyrosine in the presence of l-cysteine

In this study, a novel ordered mesoporous carbon (OMC) with high surface area (1600m2/g), large pore volume (1.6cm3/g) and open pore structure was successfully prepared by using a hard-templated method. This porous carbon material provided an amplified target-receptor interface for the electrochemical application. As a novel electrode material, the catalytic activities of OMC towards simultaneous electro-oxidation of tyrosine (Tyr) and l-cysteine (CysH) were investigated by differential pulse voltammetry. Significantly, well separated oxidation peaks of Tyr and CysH were firstly observed at physiological pH at the OMC electrode. Selective determination of Tyr was carried out in the presence of CysH. More importantly, well distinguishing Tyr from ascorbic acid, dopamine, uric acid, epinephrine was also demonstrated, suggesting an excellent anti-interference ability of this Tyr sensor in the physiological system.

Hybrids of iron oxide/ordered mesoporous carbon as anode materials for high-capacity and high-rate capability lithium-ion batteries

A hybrid of iron oxide nanoparticle modified ordered mesoporous carbon (OMC) was successfully prepared via a controllable two-step route. Electrochemical lithium storage experimental results reveal that the FeOx/OMC composites can effectively reduce the capacity decay caused by volume change, and decrease the irreversible capacity of ordered mesoporous carbon. The first discharge capacities of FeOx/OMC and OMC are 1718 mA h g−1 and 1685 mA h g−1, respectively, while the first charge capacities of the FeOx/OMC and OMC electrodes are 1004 mA h g−1 and 528 mA h g−1, respectively. Apparently, the FeOx/OMC hybrids display a higher reversible capacity of more than 660 mA h g−1 and higher initial coulombic efficiency (58.4%). More importantly, at high charge–discharge rates, even at a current density of 1600 mA g−1, the capacity of the FeOx/OMC electrode is still maintained at 320 mA h g−1 even after 50 cycles, almost 5.4 times higher than the capacity of 50 mA h g−1 for the pure OMC sample. The high rate of performance is important for applications where fast charge and discharge are needed. The prominent improvement of electrochemical performance can be attributed to the synergistic effects of the FeOx/OMC composites. The FeOx nanoparticles can reduce the large amounts of active sites due to the high specific surface of the OMC, which results in a high irreversible capacity. While the OMC in the composite not only provides an elastic buffer space to accommodate the volume expansion/contraction of FeOx nanoparticles during the Li ions insertion/extraction process, but also efficiently prevents crumbling of electrode material upon continuous cycling, thus maintaining large capacity, good Coulombic efficiency, high rate capability and cycling stability. Furthermore, the OMC in the composite with good electrical conductivity can serve as the conductive channels between FeOx nanoparticles. This excellent electrochemical performance of the FeOx/OMC hybrid makes it a candidate anode material for commercial lithium-ion batteries.

Crystalline NiFex nanoparticles homogeneously embedded in ordered mesoporous carbon for improved electrochemical hydrogen storage performance

Hybrids of bimetallic NiFex crystalline nanoparticles homogeneously embedded in ordered mesoporous carbon (OMC) for electrochemical hydrogen storage applications were fabricated through wet impregnation and H2 reduction techniques. The size and distribution of NiFex nanoparticles of NiFex/OMC hybrids can be tuned by controlling the molar ratio of Ni : Fe, with the smallest diameter of 4.7 nm for the NiFe2 alloy nanoparticles. The effects of NiFex nanoparticle incorporation into the OMC matrix on the surface area, pore volume, pore size and electrochemical hydrogen storage performances were comparatively investigated using adsorption isotherms of nitrogen, electrochemical impedance spectroscopy, potentiodynamic polarization, cyclic voltammetry and galvanostatic charge–discharge techniques. With the molar ratio of Ni : Fe decreasing, the discharge capacity and the cycle performance of the NiFex/OMC hybrids display a notable improvement due to the homogenous dispersion of NiFex nanoparticles, higher surface area, larger mesopore volume, lower defect ration, and smaller charge-transfer resistance. The NiFe2/OMC samples display greatly improved electrochemical hydrogen storage discharge capacity of 418 mA h g−1, which is about four times as high as that of the pure OMC electrode.

Influence of nitric acid modification of ordered mesoporous carbon materials on their capacitive performances in different aqueous electrolytes

Two kinds of ordered mesoporous carbon (OMC), hexagonal mesoporous carbon CMK-3 and cubic mesoporous carbon CMK-8, are prepared by a hard template nanocasting method. Afterwards, nitric acid modification is conducted to explore the influence of surface functional groups on the supercapacitive characteristics of the OMC electrodes. The electrochemical performances of CMK-3, CMK-8, acid-modified CMK-3 (H-CMK-3) and acid-modified CMK-8 (H-CMK-8) electrodes are investigated in three-electrode cells using alkaline (2M KOH), acidic (2M H2SO4) and neutral (2M Na2SO4) aqueous media. After nitric acid modification, the capacitive performances of two OMCs are improved in KOH, decreased in H2SO4, but showed no change in Na2SO4. The correlations among the change of surface functional groups after acid modification, electrolyte category and the capacitive performance of the OMCs are studied in detail. It can provide a guideline for proper usage of OMC-based materials for the next generation of supercapacitors.

Enhanced electrochemical hydrogen storage capacity of activated mesoporous carbon materials containing nickel inclusions

Electrochemical properties of activated ordered mesoporous carbon (OMC) containing nickel inclusions are investigated using cyclic voltammetry and galvanostatic charge/discharge techniques. The hard-template-route prepared OMC is of structurally well-ordered two-dimensional hexagonal structure with a high specific surface area of 1896.95 cm 2 g −1, a pore volume of 1.781 cm 3 g −1 and a pore size of 5.1 nm, respectively. It is shown that OMC/0.3Ni electrode displays the highest specific capacitance of 186.1 Fg −1, almost 1.4 times higher than that of pure OMC electrode. The hydrogen storage capacity of pure OMC electrode is 87 mAh g −1 and there exists no discharge platform. With the amount of nickel addition increasing, there appears a relatively stable discharge platform, and the discharge capacity reaches a maximum of 170 mAh g −1 as the molar ratio of Ni:OMC is 0.3, almost two times higher than that of pure OMC electrode. The electrochemical properties of OMC can be greatly improved with incorporation of nickel powders. The Ni activated OMC electrodes display a high capacity retainability with strong resistance against oxidation and corrosion.

Electrocatalytic reduction of oxygen at ordered mesoporous carbon functionalized with tetrathiafulvalene

A novel ordered mesoporous carbon-tetrathiafulvalene composite is synthesized. It is based on host-guest chemistry which utilizes synergic interactions between a nanostructured matrix of ordered mesoporous carbon (OMC) and the excellent electron donor properties of tetrathiafulvalene (TTF). It has been found that some interesting properties of OMC are improved. Especially the density of the edge plane-like defective sites, important groups responsible for the electrocatalytic activity towards some molecules, is increased on OMC-TTF composite. Moreover, this new material can be used to facilitate the heterogeneous electron transfer process. OMC-TTF was used, for the first time, to investigate the electrocatalytic reduction of oxygen. The results show that the electrocatalytic behavior of OMC-TTF is attributed to the unique physico-chemical properties of OMC and TTF. At the OMC-TTF modified electrode, the reduction proceeds by the direct four-electron pathway whereas at the OMC electrode the process is not direct. In order to show that the ability of OMC-TTF to promote the electron transfer can allow the application of this composite in many domains, an amperometric oxygen biosensor has been constructed based on OMC-TTF. It exhibits good response to dissolved oxygen with a large linear range and a very low detection limit. The interferences of ascorbic acid and uric acid are suppressed and the applied potential is positive enough to avoid perturbations of other electrochemically reducible compounds. The results above suggest that OMC-TTF has potential applications in the detection of dissolved oxygen and interesting properties of this composite may open up a new approach to study the electrochemical behavior of other biomolecules.

Effects of ferrocene derivative on the physico-chemical and electrocatalytic properties of ordered mesoporous carbon

This work reports effects of ferrocene derivative on the properties of an ordered mesoporous carbon (OMC). A novel method for the incorporation of iron oxide species in the carbon framework of OMC without any decrease in the surface area is also reported. The decomposition of ferrocene derivative yields iron species that facilitate the formation of the carbon framework. The performance of ordered mesoporous carbon containing iron oxide (OMC-Fe) is compared to OMC and the properties of the new material are found to be improved. OMC-Fe combines electrochemical properties of OMC and iron oxide species. Electrocatalytic properties towards H 2O 2 are enhanced because of synergetic effect of ordered mesoporous carbon and iron oxide species. The electrochemical determination of H 2O 2 at the OMC-Fe modified electrode is more sensitive than that at OMC electrode. A sensitive and stable H 2O 2 sensor was developed based on OMC-Fe electrode with a large determination range and a good reproducibility.

Application of electrochemical properties of ordered mesoporous carbon to the determination of glutathione and cysteine

In this study, the electrochemical activity of ordered mesoporous carbon (OMC) was investigated and applied to the determination of glutathione (GSH) and cysteine (CySH). It has been demonstrated that the ordered mesostructure of OMC has an important role in the electrocatalytic activity towards thiols, and the destruction of this structure results in the decrease of such properties. The electrochemical behavior of GSH at an OMC electrode was also investigated. The results showed that the process of oxidation of GSH at the OMC electrode is differs from that of CySH at the same electrode by the peak at 0.47 V associated with CySH. This difference helped to reduce the interference of GSH during the determination of CySH in the presence of GSH. A sensor for the two thiols was developed with acceptable sensitivity and detection limits in a large determination range. These results obtained in the physiological medium and in the physiological levels of GSH and CySH, suggest that OMC is a promising material in the detection of thiols in biologically relevant experimental conditions (in terms of pH).

Using mesoporous carbon electrodes for brackish water desalination

Electrosorptive deionisation is an alternative process to remove salt ions from the brackish water. The porous carbon materials are used as electrodes. When charged in low voltage electric fields, they possess a highly charged surface that induces adsorption of salt ions on the surface. This process is reversible, so the adsorbed salt ions can be desorbed and the electrode can be reused. In the study, an ordered mesoporous carbon (OMC) electrode was developed for electrosorptive desalination. The effects of pore arrangement pattern (ordered and random) and pore size distribution (mesopores and micropores) on the desalination performance was investigated by comparing OMC and activated carbon (AC). It were revealed from X-ray diffraction and N 2 sorption measurements that AC has both micropores and mesopores, whereas ordered mesopores are dominant in OMC. Their performance as potential electrodes to remove salt was evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests at a range of electrolyte concentrations and sweep rates. It is deduced that under the same electrochemical condition the specific capacitance values of OMC electrode (i.e. 133 F/g obtained from CV at a sweep rate of 1 mV/s in 0.1 M NaCl solution) are larger than those of AC electrode (107 F/g), suggesting that the former has a higher desalting capacity than the latter. Furthermore, the OMC electrode shows a better rate capacity than the AC electrode. In addition, the desalination capacities were quantified by the batch-mode experiment at low voltage of 1.2 V in 25 ppm NaCl solution (50 μs/cm conductivity). It was found that the adsorbed ion amounts of OMC and AC electrodes were 11.6 and 4.3 μmol/g, respectively. The excellent electrosorptive desalination performance of OMC electrode might be not only due to the suitable pore size (average of 3.3 nm) for the propagation of the salt ions, but also due to the ordered mesoporous structure that facilitates desorption of the salt. Based on the results, it was found that the development of an ordered mesoporous structure and the control of the number of micropores are two important strategies for optimising electrode material properties for electrosorptive deionisation.