Boosting Electrocatalytic Nitrate-to-Ammonia Conversion via Plasma Enhanced CuCo Alloy–Substrate Interaction

Electrocatalytic conversion of widely distributed nitrate from industrial wastewater into value-added ammonia was proposed as an attractive and sustainable alternative to harvesting green ammonia. Herein, CuCo alloys were facilely synthesized for nitrate conversion, while nonthermal Ar-plasma was employed to enhance the adhesion strength between the electrocatalyst and substrate interface via regulating the surface hydrophobicity and roughness. Based on Ar-plasma treatment, a high ammonia yield rate (5129.29 μg cm-2 h-1) was achieved using Cu30Co70 electrocatalyst -0.47 V vs RHE, while nearly 100% of Faradaic efficiency was achieved using Cu50Co50 electrocatalyst at -0.27 V vs RHE (reversible hydrogen electrode). Validated by in situ spectroscopy and density functional theory calculations, the high activity of the CuCo alloy was derived from the regulation of Co to weaken the strong adsorption capacity of Cu and the shift of the d-band center to lower the energy barrier, while Ar-plasma modification promoted the formation of *NO to boost nitrate conversion

Upcycling Waste Lard Oil into Vertical Graphene Sheets by Inductively Coupled Plasma Assisted Chemical Vapor Deposition

Vertical graphene (VG) sheets were single-step synthesized via inductively coupled plasma (ICP)-enhanced chemical vapor deposition (PECVD) using waste lard oil as a sustainable and economical carbon source. Interweaved few-layer VG sheets, H2, and other hydrocarbon gases were obtained after the decomposition of waste lard oil. The influence of parameters such as temperature, gas proportion, ICP power was investigated to tune the nanostructures of obtained VG, which indicated that a proper temperature and H2 concentration was indispensable for the synthesis of VG sheets. Rich defects of VG were formed with a high I D / I G ratio (1.29), consistent with the dense edges structure observed in electron microscopy. Additionally, the morphologies, crystalline degree, and wettability of nanostructure carbon induced by PECVD and ICP separately were comparatively analyzed. The present work demonstrated the potential of our PECVD recipe to synthesize VG from abundant natural waste oil, which paved the way to upgrade the low-value hydrocarbons into advanced carbon material

Co-generation of hydrogen and carbon aerosol from coalbed methane surrogate using rotating gliding arc plasma

A novel atmospheric pressure non-thermal plasma, i.e., rotating gliding arc (RGA), is developed to upgrade coal bed methane (CBM) into hydrogen and carbon aerosol simultaneously. CH4 is used as a CBM surrogate. In present work, the V-I characteristics of RGA discharge in CH4 conversion are monitored with different gases (N2, Ar and CO2) as carrier gas, while the active species (such as OH, CH, CN, C2, excited molecules and ions) involved in the plasma reactions are identified by optical emission spectroscopy (OES). According to the sensitivity analysis of specific energy density (SED), the importance of operating conditions on SED sensitivity is in a sequence of CH4 concentration > applied voltage > residence time. The performance of CH4 conversions are comparatively evaluated based on the variation of operating conditions. In general, the enhancement of applied voltage and residence time effectively increases the CH4 conversions, selectivity of hydrogen, as well as the energy efficiency, while the augment of CH4 concentration has a negative effect in contrast. The carbon aerosol obtained in CH4/N2 and CH4/Ar discharge are comparatively investigated. Transparent crumped-like graphene sheets and spherical nanostructure carbon are observed in both obtained carbon aerosol, with relative high ID/IG ratios (∼0.62) indicated in Raman spectroscopy. High C/O ratios (>14) are obtained in the XPS survey spectra, with the intensity ratios of sp2 C[dbnd]C/sp3 C-C occupy about 80%. However, the BET surface area of carbon obtained from CH4/N2 is almost 3 times larger than that from CH4/Ar discharge. In addition, super hydrophobic and oleophilic properties are observed in both carbon samples. The contact angles of water droplets are above 130°, while the contact angle of oil is less than 4°

Revealing the Mechanism of Dioxin Formation from Municipal Solid Waste Gasification in a Reducing Atmosphere

Gasification is an effective technology for the thermal disposal of municipal solid waste (MSW) with lower dioxin emission compared to the prevailing incineration process. Nevertheless, the mechanism of dioxin formation in the reducing atmosphere during the gasification process was seldomly explored. Herein, the effects of the atmosphere, temperature, and chlorine source were systematically investigated in terms of dioxin distribution. With CO and HO as gasification agents, a reducing reaction atmosphere was formed with abundant H which effectively suppressed the generation of C-Cl, contributing to a substantial decrease of dioxin concentration by ∼80% compared to the incineration process. The formation of dioxin was favored at temperatures below 700 °C with its peak concentration achieved at 500 °C. It was unveiled that inorganic chlorine played a dominant role in the reducing atmosphere, with a lower proportion of C-O-C/O-C═O on residual slag compared to an oxidizing atmosphere. Additionally, the generated H reduced the concentration of dioxins by attacking C-Cl and inhibiting the crucial Deacon reaction for dioxin formation, validated by density functional theory calculation. Eventually, the formation route paradigm and the reaction mechanism of dioxin formation from MSW gasification were revealed, facilitating and rationally guiding the control of dioxin emission

Low-temperature hydrogen production from waste polyethylene by nonthermal plasma (NTP)-assisted catalytic pyrolysis using NiCeOx/β catalyst

Conventional catalytic pyrolysis of waste plastics for H2 production faces challenges due to excessively high reaction temperatures. This study introduced a NiCeOx/β catalyst for low-temperature H2 production from polyethylene (PE), aiming to enhance H2 yield through nonthermal plasma (NTP) and catalytic active sites. Experimental results confirmed the efficacy of NTP in promoting collision between high-potential-energies active species and plasma-catalyst interactions, identifying acidic sites as primary catalytic active sites. Both experiments and density functional theory (DFT) calculations confirmed NiO and CeO2 particles as metallic active sites, exhibiting thermodynamic and kinetic benefits for primary products from PE pyrolysis. Under optimal conditions, the highest H2 yield and selectivity respectively reached 32.71 mmol/g and 82.10 % at a PE/(NiCeOx/β) ratio of 1:4, reaction temperature of 400 °C, and NTP discharge power of 210 W. The NiCeOx/β catalyst facilitated low-temperature pyrolysis of waste plastics, enhancing H2 selectivity and yield.</p