The development of high-efficient and low-cost oxygen reduction reaction (ORR) electrocatalysts is crucial for the practical applications of metal-air batteries. One promising way is to develop Fe single-atom catalysts. However, the single active center and inherent electronic structure of Fe single-atom catalysts lead to the undesirable adsorption of multiple ORR intermediates. Herein, a charge-asymmetry single-atom alloy (SAA) catalyst with Fe–Cu dual sites supported on nitrogen-doped carbon nanosheet (Fe₁Cu SAA/NC) was constructed. Various characterizations manifest the existence of electron interaction between Fe and Cu in Fe₁Cu SAA/NC, which facilitates the adsorption of ORR intermediate for fast kinetics. Consequently, the charge-asymmetry Fe₁Cu SAA/NC exhibits much faster ORR kinetics with a half-wave potential of 0.917 V vs. reversible hydrogen electrode (RHE), outperforming its counterparts in the references. Furthermore, Fe₁Cu SAA/NC still maintains a high half-wave potential with only a drop of 5 mV after 5000 cycles, indicating excellent stability. This work provides a new strategy to design highly active and non-noble metal ORR electrocatalysts, which hold great potential for various catalytic applications.

Twenty-three atmospheric volatile halogenated hydrocarbons (VHHs) were detected in a typical urban area of Beijing, China from 24 August to 4 September, 2012. The mean and range in daily mass concentrations of the 23 VHHs were 30.53 and 13.45–76.33 µg/m³, respectively. Seven of those VHHs were controlled ozone-depleting substances in China, with a mean of 12.95 µg/m³, accounting for 42.43% of the total. Compared with other national and international cities, the concentrations of the selected 11 VHHs in this study were relatively higher. Dichloroethane had the highest mass concentration, followed by difluorochloromethane. Maxima of total VHHs occurred within the period 8:30–9:00 a.m., while minima occurred during 1:30–2:00 p.m. Source apportionment suggested that the main sources of VHHs in the study area were solvents usage and industrial processes, leakage of chlorofluorocarbons banks, refrigerants, and fumigant usage. Among the selected 7 VHHs, trichloromethane, tetrachloromethane, 1,2-dichloroethane, and 1,4-dichlorobenzene posed potential carcinogenic risks to exposed populations, while none of the selected 11 VHHs posed appreciable non-carcinogenic risks to exposed populations. The carcinogenic risks from atmospheric VHHs in Beijing are higher than in other Chinese cities, indicating that it is necessary to implement immediate control measures for atmospheric VHHs in Beijing.

Urchin‐like Cu‐W ₁₈ O ₄₉ and flower‐like Cu‐WO ₃ structures were successfully synthesized using a hydrothermal process followed by calcination. The synthesized products were characterized using XRD, SEM, and TEM. The results revealed that the as‐prepared urchin‐like and flower‐like samples with monoclinic structures, which were approximately 1 μ m and 1‐2 μ m, respectively, possessed microflower architecture assembled by the nanosheet. In addition, the gas sensing properties of monoclinic‐structured Cu‐WO ₃ to acetone were measured using a static state gas sensing test system. The sensor based on the flower‐like Cu‐WO ₃ nanostructures, which were calcined at 600°C, exhibited high sensitivity toward 10 ppm acetone at an optimum temperature of 110°C, and the maximum sensitivity reached 40, which was approximately four times higher than that of urchin‐like WO ₃ that was annealed at 300°C. The sensitivity was improved by increasing the acetone concentration. The detection limit was as low as 1 ppm. Using linear fit, the sensor was determined to be sufficiently sensitive to detect acetone in a detection range of 1 to 10 ppm even in the presence of interfering gases, which suggests that this type of sensor has excellent selectivity and has the potential for use in acetone gas sensors in the future.

An electrocatalyst with ultra-small PtCo single atom alloy species evenly dispersed on nitrogen-doped ultra-thin carbon nanosheets (PtCo SAA/NC) was designed. The introduction of single-atom Pt not only maximizes the atomic utilization efficiency of Pt species, but also synergistically enhances the charge transfer characteristics of Co cluster surfaces, thereby increasing the migration and evolution rate of hydrogen ions. The PtCo SAA/NC catalyst exhibits a Tafel slope of 42 mV dec⁻¹ and a low overpotential of 45 mV at 10 mA cm⁻² in 0.5 M H₂SO₄ solution.

In this study, NaClO₂ was used as an oxidant and mixed with NaOH to prepare a sodium-based composite absorbent. Simultaneous desulfurization and denitrification experiments were conducted in an ultrasonic atomization reactor and the effects of experimental parameters including pH value, NaClO₂ concentration, initial concentration of NO, reaction temperature, the addition of SO2 and the utilization of ultrasonic atomization on desulfurization and denitrification efficiencies were investigated. Under the circumstance of the pH of 10, oxygen content of 8%, reaction temperature of 55oC, and NO concentration of 500 mg/m³, SO₂ concentration of 1400 mg/m3, 69.38% of NO and 99.95% of SO₂ can be removed using the composite absorbent composed of 0.02 mol/L NaClO2 and 0.1mmol/L NaOH. Ultrasonic atomization increased the denitrification rate by 10.6%.