No abstract

The adsorption of methane on an activated carbon of high surface was measured in the range of 233−333 K and 0−10 MPa. The isotherms showed a considerably different feature than that measured on low surface carbon. A maximum appeared on isotherms at relatively low temperatures. All the experimental isotherms were well modeled by the Langmuir−Freundlich equation. The difference between the measured and the so-called absolute adsorption was properly accounted for in modeling. An assumption of monolayer adsorbate adsorbed was included in the model. The layer volume evaluated was consistent with the pore volume of adsorbent reported by CO2 adsorption. The intermolecular distance in the adsorbed phase was evaluated from a model parameter. This intermolecular distance was compared with that in the free sate, which revealed a basic picture of the physical state of the adsorbed phase at above-critical temperatures.

The influence of alumina binder on the catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation was studied. Solid-state 27Al MAS NMR spectroscopy, temperature-programmed desorption of ammonia (TPDA), temperature-programmed oxidation (TPO), catalytic grain intensity, hydrogen chemisorption, BET surface area, and pore size distribution measurements were used to characterize the catalysts. It was found that the addition of binder results in a decrease in the surface area of the catalyst but an obvious improvement in its particle intensity. Some soluble Al species from the binder might migrate into the ZSM-5 zeolite framework during calcination so as to produce some acid sites of moderate intensity, which consequently increases the acid amount of the catalyst. When propane dehydrogenation is carried out under the same space velocity by changing the weight of the corresponding catalyst, the acid amount is the dominant factor influencing the catalytic properties. When this reaction is performed under the same catalyst weight, a small amount of binder is seen to have a positive effect, increasing the catalytic activity as a result of the enhanced metal dispersion and acid amount. However, a negative effect is observed when the binder amount continues to increase. The function of stabilizing the tin species can be strengthened by alumina addition, which might facilitate the transport of the carbon deposits from the active sites to the carrier. TPO profiles of the corresponding catalysts under different reaction conditions represent dissimilar behaviors, which is attributed to an increase in acid amount and change in metal dispersion in the presence of binder. Finally, a model for the influence of the alumina binder on the catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation is proposed.

Effectively improving the selectivity while reducing the overpotential over the electroreduction of CO2 (CO2ER) has been challenging. Herein, electronegative N atoms and coordinatively unsaturated NiN3 moieties co‐anchored carbon nanofiber (NiN3NCNFs) catalyst via an integrated electrospinning and carbonization strategy are reported. The catalyst exhibits a maximum CO Faradaic efficiency (F.E.) of 96.6%, an onset potential of −0.3 V, and a low Tafel slope of 71 mV dec−1 along with high stability over 100 h. Aberration corrected scanning transmission electron microscopy, X‐ray absorption spectroscopy, and X‐ray photoelectron spectroscopy identify the atomically dispersed NiN3 sites with Ni atom bonded by three pyridinic N atoms. The existence of abundant electronegative N dopants adjoin the NiN3 centers in NiN3NCNFs. Theoretical calculations reveal that both, the undercoordinated NiN3 centers and their first neighboring C atoms modified by extra N dopants, display the positive effect on boosting CO2 adsorption and water dissociation processes, thus accelerating the CO2ER kinetics process. Furthermore, a designed ZnCO2 battery with the cathode of NiN3NCNFs delivers a maximum power density of 1.05 mW cm−2 and CO F.E. of 96% during the discharge process, thus providing a promising approach to electric energy output and chemical conversion.

Zinc oxide (ZnO) nanofibers with an average diameter of 150 nm were synthesized by electrospinning. The morphology and structure of the as‐prepared ZnO nanofibers have been characterized by scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction, respectively. The as‐prepared ZnO nanofibers exhibit excellent sensing properties against ethanol at an operating temperature of 300°C, including a rapid response (time ∼3 s) and recovery (time ∼8 s), super sensitivity, and high selectivity, which makes our product a good candidate for fabricating gas sensors in practice.