SnS2/MWNTs/sponge electrode combined with plasma dielectric barrier discharge catalytic system: CO2 reduction and pollutant degradation.

SnS2 nanosheets combined with multi-walled carbon nanotubes (MWNTs) were made into sponge electrodes which were used for CO2 reduction reaction (CO2RR) in dielectric barrier discharges (DBD) system. The amounts of formate and formaldehyde produced by CO2 reduction with SnS2/MWNTs/sponge electrode were 299.52 and 31.62 µmol h-1, which were higher than that of MWNTs/sponge electrodes. The addition of pollutants had different degrees of inhibitory effect on CO2 reduction, among which addition of bisphenol A (BPA) had the smallest effect that the degradation rate of BPA was 94.37% and the C1 products remained 204.43 µmol after 60 min discharge. The mechanism of CO2RR was studied by quencher experiment, and the main contribution order of the active substance in DBD system for CO2RR is: H+>e->·OH>·O2-. It was found that the degradation process of pollutants consumed H+ and e- in solution, thereby inhibiting CO2RR. Generally, the SnS2/MWNTs/sponge electrode provided a reference for the design of catalysts for CO2 reduction and pollutant degradation in plasma gas-liquid system.

ZnCo2O4 composite catalyst accelerated removal of phenylic contaminants containing of Cr(VI) in dielectric barrier discharge reactor: Process and mechanism study.

The degradation of phenylic contaminants (phenol, hydroquinone, nitrobenzene, p-nitrophenol) containing Cr(VI) has been investigated in a dielectric barrier discharge (DBD) system using a ZnCo2O4 composite catalyst. The ZnCo2O4 nanowires combined with multi-walled carbon nanotubes (MWNTs) on a sponge substrate in the discharge system can induce a decrease in the corona inception voltage and discharge becomes more stable resulting in an improvement in the energy utilization efficiency. With the synergistic degradation of phenylic species containing Cr(VI), the total elimination efficiency was further improved. The active substances (H2O2 and O3) were detected in the discharged solution, and some of them were consumed in the phenylic system. The effects of ·OH, O2·- and e- were also verified using free radical trapping experiments in which ·OH exhibited the main oxidation effect for the degradation of phenylic pollutants, and e-, H2O2 and H· affect the reduction of Cr(VI). The intermediate products were determined in order to analyze the degradation process of phenylic pollutants by the ZnCo2O4 composite catalyst in combination with the DBD system. The electron transfer process in the ZnCo2O4 composite catalyst during discharge was analyzed. Finally, the biotoxicity of the phenylic pollutants before and after degradation was compared.

Promoting the reduction of CO2 to formate and formaldehyde via gas-liquid interface dielectric barrier discharge using a Zn0.5Cd0.5S/CoP/multiwalled carbon nanotubes catalyst.

A Zn0.5Cd0.5S (ZCS) solid solution was prepared using a hydrothermal method, in which CoP nanowires were added as a co-catalyst and co-deposited with multiwalled carbon nanotubes (MWNTs) on sponge to prepare a series of ZCS/CoP/MWNTs/sponge electrodes. The microstructures of catalysts were analyzed to confirm ZCS and CoP were successfully loaded in MWNTs/sponge. The CO2 reduction products (formate and formaldehyde) produced via dielectric barrier discharge (DBD) using the different catalysts proved that the introduction of the CoP nanowires co-catalyst can enhance the catalytic activity of ZCS/MWNTs/sponge in the DBD system. Using 10% CoP and a ZCS/CoP concentration of 2.5 g·L-1, the resulting ZCS/CoP/MWNTs/sponge catalyst exhibited the best catalytic of CO2 reduction ability toward formate (7894.6 µmol·L-1) and formaldehyde (308.5 µmol·L-1) after 60 min of discharge, respectively. The proposed DBD catalytic mechanism for the reduction of CO2 was analyzed according to the Tafel slope, density functional theory calculations, photocurrent density and plasma reaction process. Furthermore, the application of the DBD catalytic technology for CO2 capture and reduction was shown to be efficient in a seawater system, and as such, it could be useful for marine CO2 storage and conversion.

Dielectric barrier discharge plasma-assisted modification of g-C3N4/Ag2O/TiO2-NRs composite enhanced photoelectrocatalytic activity.

Dielectric barrier discharge (DBD) plasma applied as surface treatment technology was employed for the modification of Ag2O and graphitic carbon nitride (g-C3N4) powders. Subsequently, the pretreated powders were sequentially loaded onto TiO2 nanorods (TiO2-NRs) via electro-deposition, followed by calcination at N2 atmosphere. The results indicated that at the optimal plasma discharge time of 5 min for modification of g-C3N4 and Ag2O, photocurrent density of ternary composite was 6 times to bare TiO2-NRs under UV-visible light irradiation. Phenol was degraded by using DBD plasma-modified g-C3N4/Ag2O/TiO2-NRs electrode to analyze the photoelectrocatalytic performance. The removal rate of phenol for g-C3N4-5/Ag2O-5/TiO2-NRs electrode was about 3.07 times to that for TiO2-NRs electrode. During active species scavengers' analysis, superoxide radicals and hydroxyl radicals were the main oxidation active species for pollutants degradation. A possible electron-hole separation and transfer mechanism of ternary composite with high photoelectrocatalytic performance was proposed.

CuO@Cu/Ag/MWNTs/sponge electrode-enhanced pollutant removal in dielectric barrier discharge (DBD) reactor.

In this study, a sponge modified by multi-walled carbon nanotubes (MWNTs) was used as sheet support for the adsorption of CuO@Cu and Ag nanowires to prepare a CuO@Cu/Ag/MWNTs/sponge electrode. Similar to their use in a dielectric barrier discharge (DBD) reactor, the MWNTs changed the conductivity and water absorptivity of the modified electrode, whereas the CuO@Cu and Ag nanowires significantly enhanced the tip effect to increase discharge. The optimal ratio of the Ag:CuO@Cu nanowires was 5:3 at a total adsorbed concentration of 0.8 g L-1. Compared with CuO@Cu and Ag nanowires were separately adsorbed on the MWNTs/sponge, and the CuO@Cu/Ag/MWNTs/sponges recorded higher current response, lower discharge inception voltage, and higher removal efficiency of phenol and 2,4,5-trichlorobiphenyl (PCB29) through their degradation. The removal efficiency reached 100% within 30 min of the reaction for the degradation of phenol and 65.1% within 60 min of the reaction for the degradation of PCB29 at an input voltage of 30 V. These results show that the CuO@Cu/Ag/MWNTs/sponge structure has significant potential for use in the DBD reactor to improve the discharge efficiency of the system and reduce energy consumption, and can be further extended to other types of plasma reactors.