High-Throughput NOx Removal by Two-Stage Plasma Honeycomb Monolith Catalyst.

A two-stage plasma catalyst system for high-throughput NOx removal was investigated. Herein, the plasma stage involved the large-volume plasma discharge of humidified gas and was carried out in a sandwich-type honeycomb monolith reactor consisting of a commercial honeycomb catalyst (50 mm high; 93 mm in diameter) located between two parallel perforated disks that formed the electrodes. The results demonstrated that, in the plasma stage, the reduction of NOx did not occur at room temperature; instead, NO was only oxidized to NO2 and n-heptane to oxygenated hydrocarbons. The oxidation of NO and n-heptane in the honeycomb plasma discharge state was largely affected by the humidity of the feed gas. Furthermore, the oxidation of NO to NO2 occurs preferably to that of n-heptane with a tendency of the NO oxidation to decrease with increasing feed gas humidity. The reason is that the generation of O3 decreases as the amount of water vapor in the feed gas increases. Compared to the catalyst alone, the two-stage plasma catalyst system increased NOx removal by 29% at a temperature of 200 °C and an energy density of 25 J/L.

Synergistic Performance Boosts of Dopamine-Derived Carbon Shell Over Bi-metallic Sulfide: A Promising Advancement for High-Performance Lithium-Ion Battery Anodes.

A CoMoS composite is synthesized to combine the benefits of cobalt and molybdenum sulfides as an anodic material for advanced lithium-ion batteries (LIBs). The synthesis is accomplished using a simple two-step hydrothermal method and the resulting CoMoS nanocomposites are subsequently encapsulated in a carbonized polydopamine shell. The synthesis procedure exploited the self-polymerization ability of dopamine to create nitrogen-doped carbon-coated cobalt molybdenum sulfide, denoted as CoMoS@NC. Notably, the de-lithiation capacity of CoMoS and CoMoS@NC is 420 and 709 mAh g⁻1, respectively, even after 100 lithiation/de-lithiation cycles at a current density of 200 mA g⁻1. Furthermore, excellent capacity retention ability is observed for CoMoS@NC as it withstood 600 consecutive lithiation/de-lithiation cycles with 94% capacity retention. Moreover, a LIB full-cell assembly incorporating the CoMoS@NC anode and an NMC-532 cathode is subjected to comprehensive electrochemical and practical tests to evaluate the performance of the anode. In addition, the density functional theory showcases the increased lithium adsorption for CoMoS@NC, supporting the experimental findings. Hence, the use of dopamine as a nitrogen-doped carbon shell enhanced the performance of the CoMoS nanocomposites in experimental and theoretical tests, positioning the material as a strong candidate for LIB anode.

A simple microplasma reactor paired with indirect ultrasonication for aqueous phase synthesis of cobalt oxide nanoparticles.

Cobalt oxide nanoparticles are widely used owing to their distinct properties such as their larger surface area, enhanced reactivity, and their superior optical, electronic, and magnetic properties when compared to their bulk counterpart. The nanoparticles are preferably synthesized using a bottom-up approach in liquid as it allows the particle size to be more precisely controlled. In this study, we employed microplasma to synthesize Co3O4 nanoparticles because it eliminates harmful reducing agents and is efficient and cost-effective. Microplasma reactors are equipped with copper wire electrodes to generate plasma and are simple to configure. The product was characterized using UV-Vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The experimental parameters that were varied for the synthesis were: with or without stirring, with or without indirect ultrasonication, and with or without capping agents (urea and sucrose). The results showed that the microplasma enabled Co3O4 nanoparticles to be successfully synthesized, with particle sizes of 10.9-17.7 nm, depending on the synthesis conditions.

Activated carbon derived from cherry flower biowaste with a self-doped heteroatom and large specific surface area for supercapacitor and sodium-ion battery applications.

Herein, cherry flower waste-derived activated carbon (CFAC) with self-doped nitrogen is synthesized as a viable energy storage material for green and sustainable energy solutions. The activated carbon derived in this way is examined as an electric double-layer capacitance (EDLC)-type electrode material and sodium-ion battery (NIB) electrode material, and commendable performance is demonstrated for both of these energy storage applications. The specific surface area (SSA) and nitrogen content are observed to play a very delicate role in determining the charge storage ability of the CFAC, and the performance is optimized only by carefully balancing both of these properties. The optimized CFAC electrode supplied an excellent performance with a specific capacitance of 333.8 F g-1 and capacity is maintained to more than 96% even after 38,000 charge-discharge cycles as an EDLC-type supercapacitor electrode material. Likewise, the CFAC/NIB also yielded remarkable performance with an average specific capacity of 150 mAh g-1 and capacity retention of more than 84% after 200 charge-discharge cycles. Furthermore, an electrokinetic study was performed for both supercapacitor and NIB applications to identify the contribution from surface and diffusion type charge storage phenomena, consequently highlighting the role of the SSA and nitrogen content in the CFAC matrix.

Plasma-catalytic ethylene removal by a ZSM-5 washcoat honeycomb monolith impregnated with palladium.

The effective removal of dilute ethylene in a novel honeycomb plasma reactor was investigated using a honeycomb catalyst (Pd/ZSM-5/monolith) sandwiched between two-perforated electrodes operating at ambient temperature. Herein, the dependence of catalyst performance on the binder fraction, catalyst preparation method, and catalyst loading was examined. Ethylene removal was carried out by a process comprising cycles of 30-min adsorption conjugated with 15-min plasma-catalytic oxidation. Interestingly, the performance of the cyclic process was superior to continuous plasma-catalytic oxidation and thermally activated catalyst in terms of energy conservation, i.e., ~36 compared to ~105 and ~300 J/L, respectively. Hence, the novel cyclic process can be considered advanced-oxidation technology that features room-temperature oxidation, offers low energy consumption, negligible hazardous by-products emissions such as NOx and O3. Moreover, the process operated under described conditions: low-pressure drop, ambient atmosphere, a mechanically stable system, and a simple reactor configuration, suggesting the practical applicability of this plasma process.

Effective practical removal of acetaldehyde by a sandwich-type plasma-in-honeycomb reactor under surrounding ambient conditions.

The effective removal of acetaldehyde by humidified air plasma was investigated with a high throughput of contaminated gas in a sandwiched honeycomb catalyst reactor at surrounding ambient temperature. Here, acetaldehyde at the level of a few ppm was successfully oxidized by the honeycomb plasma discharge despite the harsh condition of large water content in the feed gas. The conversion rate of acetaldehyde increased significantly with the presence of catalysts coating on the surface channels. The increased conversion rate was also obtained with a high specific energy input (SEI) and total flow rate. Interestingly, the conversion changed negligibly under the acetaldehyde concentration range from 5 to 20 ppm. However, the conversion rate decreased toward increased water amount in the feed gas. Notably, about 60% of acetaldehyde in the feed was oxidized under SEI of 40 J/L at water amounts ≤ 2.5%, approximately 0.5 g/kWh for acetaldehyde removal. Also, the plasma-catalyst reaction was superior to the thermal reactive catalyst for acetaldehyde removal in airborne pollutants. In comparison with other plasma-catalyst sources for acetaldehyde removal, the energy efficiency under the condition is comparable. Moreover, the honeycomb plasma discharge features high throughput, avoiding pressure drop, and straightforward reactor configuration, suggesting potential practical applications.

Removal of ethyl acetate in air by using different types of corona discharges generated in a honeycomb monolith structure coated with Pd/γ-alumina.

A method based on the corona discharge produced by high voltage alternating current (AC) and direct current (DC) over a Pd/γ-Al2O3 catalyst supported on a honeycomb structure monolith was developed to eliminate ethyl acetate (EA) from the air at atmospheric pressure. The characteristics of the AC and DC corona discharge generated inside the honeycomb structure monolith were investigated by varying the humidity, gas hourly space velocity (GHSV), and temperature. The results showed that the DC corona discharge is more stable and easily operated at different operating conditions such as humidity, GHSV, and gas temperature compared to the AC discharge. At a given applied voltage, the EA conversion in the DC honeycomb catalyst discharge is, therefore, higher compared with that in the AC honeycomb catalyst discharge (e.g., 96% of EA conversion compared with approximately 68%, respectively, at 11.2 kV). These new results can open opportunities for wide applications of DC corona discharge combined with honeycomb catalysts to VOC treatment.

Dependence of humidified air plasma discharge performance in commercial honeycomb monoliths on the configuration and key parameters of the reactor.

The effect of the reactor configuration and several key parameters such as the gas temperature, humidity, and flow rate on the corona discharge plasma in honeycomb monoliths was investigated. The AC corona discharge-based plasma reactor consisted of two parallel electrodes (perforated disk/wire-mesh) placed at both ends of the honeycomb monolith. Although the wire-mesh electrode offers increased sharpness, the perforated disk electrode, where the corona discharge started at the sharp edges of the holes, produced more discharge power because of the larger effective electrode area. Loading a small amount of metal onto the monolith was found to increase the discharge power significantly. Coating the monolith with a zeolite such as ZSM-5 (Si/Al: 23.9) led to a decrease in the discharge power because of its hydrophobic nature and large surface area. The result also revealed that the operating temperature, the humidity of the feed gas, and the gas velocity were key factors affecting the discharge performance. The discharge power was inversely proportional to the temperature. On the other hand, the use of a high-velocity feed gas with high water vapor content was found to be particularly advantageous for obtaining high discharge power.

Synergistic effects of nanocarbon spheres sheathed on a binderless CoMoO4 electrode for high-performance asymmetric supercapacitor.

An essential key to enhancing the specific capacity and cyclic stability of transition metal oxide materials is the hybridization of carbon compounds by binder-free methods for supercapacitors. Carbonaceous compounds shorten the electron-ion diffusion pathways due to their high active surface area and conductivity. Herein, we focus on improving the specific energy, stability, and conductivity of the electrode by the incorporation of nanosized carbon material. The integration of nano carbons from viable eco-friendly glucose with CoMoO4 enhanced the experimental specific capacity of the electrode. The self-grown CoMoO4 on a nickel foam (CMO-NF) was confirmed as the best approach after extensive optimization process by the feasible hydrothermal (HT) method. The amount of carbon deposited and the structural morphology on the fabricated CoMoO4-glucose-derived carbon (CMO-GC) electrode was varied by adjusting the concentration of glucose by the viable HT technique. Notably, the hybrid CMO-GC-2 achieved a maximum specific capacity of 851.85 C g-1 at 1 A g-1, and it is relatively higher than that of CMO-NF (301.4 C g-1). The asymmetric supercapacitor device (CMO-GC-2//AC) demonstrated excellent energy density (36.86 W h kg-1 for 152.84 W kg-1), power density (3209.35 W kg-1 for 11.19 W h kg-1), and extensive capacity retention of 87% for up to 5000 cycles. The high performance is related to the synergetic effect of EDLC and the redox reaction, with nano-architecture and well-defined morphology of the electrode material.