High spatiotemporal resolution ammonia emission inventory from typical industrial and agricultural province of China from 2000 to 2020.

As a typical industrial and agricultural province, Shandong is one of China's most seriously air-polluted regions. One comprehensive ammonia emission inventory with a high spatial resolution (1 km × 1 km) for 136 county-level administrative divisions in Shandong from 2000 to 2020 is developed based on county-level activity data with the corrected and updated emission factors of seventy-seven subcategories. Annual ammonia emissions decrease from 1003.3 Gg in 2000 to 795.9 Gg in 2020, with an annual decrease rate of 1.2 %. Therein, the ammonia emissions associated with livestock and farmland ecosystems in 2020 account for 50.8 % and 32.9 % of the provincial total ammonia emission, respectively. Laying hen and wheat are the livestock and crop with the highest ammonia emissions, accounting for 23.3 % and 36.3 % of ammonia emissions from livestock and the application of synthetic fertilizers, respectively. Furthermore, waste treatment, humans and vehicles are the top three ammonia emission sources in urban areas, accounting for 5.0 %, 4.7 % and 1.3 % of total ammonia emissions, respectively. The spatial distribution of grids with high ammonia emissions is consistent with the distribution of intensive farms. Significant emission intensity areas mainly concentrate in western Shandong (e.g., Caoxian of Heze, Qihe of Dezhou, Yanggu of Liaocheng, Liangshan of Jining) due to the large area of arable land and the high levels of agricultural activity. Overall, prominent seasonal variability characteristics of ammonia emission are observed. Ammonia emissions tend to be high in summer and low in winter, and the August to January-emission ratio is 5.6. The high temperature and fertilization for maize are primarily responsible for Shandong's increase in ammonia emissions in summer. Finally, the validity of the estimates is further evaluated using uncertainty analysis and comparison with previous studies. This study can provide information to determine preferentially effective PM2.5 control strategies.

Selective Electroreduction of 5-Hydroxymethylfurfural to Dimethylfuran in Neutral Electrolytes via Hydrogen Spillover and Adsorption Configuration Adjustment.

5-Hydroxymethylfurfural (HMF), one of the essential C6 biomass derivatives, has been deeply investigated in electrocatalytic reduction upgrading. Nevertheless, the high product selectivity and rational design strategy of electrocatalysts for electrocatalytic HMF reduction is still a challenge. Here, a high selective electro-reduction of HMF to dimethylfuran (DMF) on palladium (Pd) single atom loaded on titanium dioxide (Pd SA/TiO2 ) via hydrogen spillover and adsorption configuration adjustment in neutral electrolytes is achieved. Combining density functional theory calculations and in situ characterization, it is revealed that Pd single atom could weaken the interaction between Pd atoms and adsorbed hydrogen (*H) to promote the *H spillover for increasing *H coverage on the surface and maintain the tilted adsorption configuration to activate C═O bond; thus the selectivity of DMF on Pd SA/TiO2 increases to 90.33%. Besides, it is elaborated that low *H coverage on TiO2 favors the formation of bis(hydroxymethyl)hydro-furoin (BHH), and the flat adsorption configuration of HMF on Pd nanoparticles benefits to form 2,5-dihydroxymethylfuran (DHMF). This work provides a promising approach for modifying electrocatalysts to realize the selective electroreduction of HMF to value-added products.

S-scheme MOF-on-MOF heterojunctions for enhanced photo-Fenton Cr(VI) reduction and antibacterial effects.

The photocatalytic efficiency is commonly restrained by inferior charge separation rate. Herein, the S-scheme MIL-100(Fe)/NH2-MIL-125(Ti) (MN) photo-Fenton catalyst with the built-in electric field (BEF) was successfully constructed by a simple ball-milling technique. As a result, the MN-3 (the mass ratio of MIL-100(Fe) to NH2-MIL-125(Ti) was 3) composite presented the best visible-light-induced photocatalytic ability, in contrast to pure MIL-100(Fe) and NH2-MIL-125(Ti). The reduction efficiency of Cr(VI) almost reached 100% within 35 min of illumination. Moreover, the MN-3 heterojunction also exhibited the highest antibacterial activity, and about 100% E. coli and more than 90% S. aureus were killed within 60 min of illumination. In photo-Fenton system, In the photo-Fenton system, e-, O2•- and Fe2+ played vital roles for Cr(VI) reduction, and •OH, h+ and O2•- and 1O2 were responsible for sterilization. Additionally, 5 cyclic tests and relevant characterizations confirmed the excellent repeatability and stability of the composite. Also, the S-scheme charge transfer process was put forward. This work offers a novel idea for establishing the MOF-on-MOF photo-Fenton catalyst for high-efficiency environmental mitigation.

Electrocatalytic Synthesis of Nylon-6 Precursor at Almost 100 % Yield.

Synthesis of cyclohexanone oxime via the cyclohexanone-hydroxylamine process is widespread in the caprolactam industry, which is an upstream industry for nylon-6 production. However, there are two shortcomings in this process, harsh reaction conditions and the potential danger posed by explosive hydroxylamine. In this study, we presented a direct electrosynthesis of cyclohexanone oxime using nitrogen oxides and cyclohexanone, which eliminated the usage of hydroxylamine and demonstrated a green production of caprolactam. With the Fe electrocatalysts, a production rate of 55.9 g h-1 gcat -1 can be achieved in a flow cell with almost 100 % yield of cyclohexanone oxime. The high efficiency was attributed to their ability of accumulating adsorbed hydroxylamine and cyclohexanone. This study provides a theoretical basis for electrocatalyst design for C-N coupling reactions and illuminates the tantalizing possibility to upgrade the caprolactam industry towards safety and sustainability.

Dynamic Reconstitution Between Copper Single Atoms and Clusters for Electrocatalytic Urea Synthesis.

Electrocatalytic CN coupling between carbon dioxide and nitrate has emerged to meet the comprehensive demands of carbon footprint closing, valorization of waste, and sustainable manufacture of urea. However, the identification of catalytic active sites and the design of efficient electrocatalysts remain a challenge. Herein, the synthesis of urea catalyzed by copper single atoms decorated on a CeO2 support (denoted as Cu1 -CeO2 ) is reported. The catalyst exhibits an average urea yield rate of 52.84 mmol h-1 gcat. -1 at -1.6 V versus reversible hydrogen electrode. Operando X-ray absorption spectra demonstrate the reconstitution of copper single atoms (Cu1 ) to clusters (Cu4 ) during electrolysis. These electrochemically reconstituted Cu4 clusters are real active sites for electrocatalytic urea synthesis. Favorable CN coupling reactions and urea formation on Cu4 are validated using operando synchrotron-radiation Fourier transform infrared spectroscopy and theoretical calculations. Dynamic and reversible transformations of clusters to single-atom configurations occur when the applied potential is switched to an open-circuit potential, endowing the catalyst with superior structural and electrochemical stabilities.

High spatiotemporal resolution vehicular emission inventory in Beijing-Tianjin-Hebei and its surrounding areas (BTHSA) during 2000-2020, China.

One comprehensive emission inventory of CO, HC, NOX, PM10, PM2.5, BC, CH4, CO2 and N2O with high spatial resolution (0.01° × 0.01°) for 58 cities in Beijing-Tianjin-Hebei and its surrounding areas (BTHSA) during 2000-2020 are developed by using COPERT model and ArcGIS methodology. The results show that vehicular emissions of CO, HC, NOX, PM10, PM2.5, BC and CH4 have begun to decrease or slow their growth rates in recent years due to the implementation of measures to control vehicular emissions. However, vehicular emissions of CO2 increase rapidly due to little fuel economy improvement. Besides, the usage of selective catalytic reduction (SCR) systems by heavy duty truck (HDT) is the main factor impacting the growth trend of vehicular N2O emissions since 2017. By 2020, vehicular emissions of CO, HC, NOX, PM10, PM2.5, BC, CO2, CH4 and N2O are estimated at about 1.65 Mt, 0.35 Mt, 1.39 Mt, 87.44 kt, 55.06 kt, 15.57 kt, 527.71 Mt, 36.20 kt and 8.56 kt, respectively. Therein, China III, IV, IV and IV passenger cars (PCs) are the predominated models for vehicular emissions of CO, HC, CH4 and CO2, accounting for 19.59-28.26 % of the total vehicular emission of corresponding pollutant. Nevertheless, the major contributors of vehicular emissions of NOX, PM10, PM2.5, BC and N2O are China III (29.64 %), III (18.03 %), III (22.81 %), III (42.16 %) and V (22.28 %) HDTs, respectively. The gridded vehicular emissions vary significantly, with emissions of CO, HC, CH4 and CO2 being mainly concentrated in central urban areas of cities (e.g., Beijing, Tangshan, Zhengzhou, Tianjin, Qingdao, Jinan). Nevertheless, the grids with high vehicular emissions of NOX, PM10, PM2.5, BC and N2O are mainly distributed along the expressway and the suburban roads of cities (e.g., Linyi, Tangshan, Jining, Weifang, Shijiazhuang, Tianjin, Baoding). Finally, multi-year uncertainties of vehicular emission inventory are discussed.

Identifying and tailoring C-N coupling site for efficient urea synthesis over diatomic Fe-Ni catalyst.

Electrocatalytic urea synthesis emerged as the promising alternative of Haber-Bosch process and industrial urea synthetic protocol. Here, we report that a diatomic catalyst with bonded Fe-Ni pairs can significantly improve the efficiency of electrochemical urea synthesis. Compared with isolated diatomic and single-atom catalysts, the bonded Fe-Ni pairs act as the efficient sites for coordinated adsorption and activation of multiple reactants, enhancing the crucial C-N coupling thermodynamically and kinetically. The performance for urea synthesis up to an order of magnitude higher than those of single-atom and isolated diatomic electrocatalysts, a high urea yield rate of 20.2 mmol h-1 g-1 with corresponding Faradaic efficiency of 17.8% has been successfully achieved. A total Faradaic efficiency of about 100% for the formation of value-added urea, CO, and NH3 was realized. This work presents an insight into synergistic catalysis towards sustainable urea synthesis via identifying and tailoring the atomic site configurations.

Oxygen Vacancy-Mediated Selective C-N Coupling toward Electrocatalytic Urea Synthesis.

The electrocatalytic C-N coupling for one-step urea synthesis under ambient conditions serves as the promising alternative to the traditional urea synthetic protocol. However, the hydrogenation of intermediate species hinders the efficient urea synthesis. Herein, the oxygen vacancy-enriched CeO2 was demonstrated as the efficient electrocatalyst with the stabilization of the crucial intermediate of *NO via inserting into vacant sites, which is conducive to the subsequent C-N coupling process rather than protonation, whereas the poor selectivity of C-N coupling with protonation was observed on the vacancy-deficient catalyst. The oxygen vacancy-mediated selective C-N coupling was distinguished and validated by the in situ sum frequency generation spectroscopy. The introduction of oxygen vacancies tailors the common catalyst carrier into an efficient electrocatalyst with a high urea yield rate of 943.6 mg h-1 g-1, superior than that of partial noble-metal-based electrocatalysts. This work provides novel insights into the catalyst design and developments of coupling systems.

Speciation of phosphorus in plant- and manure-derived biochars and its dissolution under various aqueous conditions.

Phosphorus (P) in biochar serves as both a P source for plant growth and a contributor to water eutrophication, thus prioritizing the efficient management of P in biochar. This study employed solid- and solution- state 31P-nuclear magnetic resonance and X-ray diffraction analyses to explore the impact of feedstock and heating treatment temperature (HTT) on P species of biochars. The effects of ambient temperature, coexisting anions, pH and nutrient solution on P release were also investigated to study the effect of various environmental factors on P release from biochars. P species in both plant- and manure- derived biochars were dominated by inorganic orthophosphate and pyrophosphate (mainly calcium-bound-phosphates). The HTT of biochar showed a negative impact upon its pyrophosphate content. Compared with plant biochars, manure biochars contained higher P but had a lower release degree. Release of P from biochars was controlled by diffusion-dissolution process and was enhanced by higher ambient temperature, co-existing anions, and both acidic and alkaline conditions but inhibited by coexisting Hoagland nutrients. Anion-induced increase in P release was more significant for plant biochars than manure biochars. These findings help to adjust favorable environmental conditions for the full utilization of P in biochars.

Metal/metalloid elements and polycyclic aromatic hydrocarbon in various biochars: The effect of feedstock, temperature, minerals, and properties.

Fourteen metal/metalloid elements and sixteen polycyclic aromatic hydrocarbons (PAHs) within biochars were quantified to investigate how heat treatment temperatures (HTTs) and feedstocks affect their concentration and composition. Concentrations and composition of metals/metalloids were strongly dependent upon feedstocks rather than HTTs. HTTs significantly affected concentrations and composition of PAHs. The highest concentration of PAHs was observed for plant residue-derived biochars (PLABs) produced at 450 °C and the opposite result was for animal waste-derived bichars. High mineral content was responsible for depolymerization of organic matter (OM), which facilitated high production of PAHs. High HTTs pyrolysis or combustion PAHs (COMB) of PLABs possibly blocks their micropores derived from other components within OM and leads to a decline of CO2-surface areas (CO2-SAs). Concentration of ∑COMB or individual PAH was affected by biochar properties, including composition and contents of functional groups, ash content, and CO2-SAs. PLABs produced at 600 °C were recommended for low toxicity.

Properties of the plant- and manure-derived biochars and their sorption of dibutyl phthalate and phenanthrene.

The properties of plant residue-derived biochars (PLABs) and animal waste-derived biochars (ANIBs) obtained at low and high heating treatment temperatures (300 and 450°C) as well as their sorption of dibutyl phthalate (DBP) and phenanthrene (PHE) were investigated in this study. The higher C content of PLABs could explain that CO2-surface area (CO2-SA) of PLABs was remarkably high relative to ANIBs. OC and aromatic C were two key factors influencing the CO2-SA of the biochars. Much higher surface C content of the ANIBs than bulk C likely explained that the ANIBs exhibited higher sorption of DBP and PHE compared to the PLABs. H-bonding should govern the adsorption of DBP by most of the tested biochars and π-π interaction play an important role in the adsorption of PHE by biochars. High CO2-SA (>200 m(2) g(-1)) demonstrated that abundant nanopores of OC existed within the biochars obtained 450°C (HTBs), which likely result in high and nonlinear sorption of PHE by HTBs.

The opposite impacts of Cu and Mg cations on dissolved organic matter-ofloxacin interaction.

Dialysis equilibrium system was applied to investigate the roles of Cu(II) and Mg(II) on DOM-ofloxacin (OFL) interaction. The binding behavior of both cations and OFL were studied. The introduction of Cu(II) increased DOM-OFL interaction, while Mg(II) decreased DOM-OFL binding. Cu(II) binding to DOM was also increased by OFL, while Mg(II) binding was decreased by OFL. The change in OFL binding amount in the absence and presence of cations (ΔC(b)) was calculated and compared with cation binding (C(b)(m)). ΔC(b)/C(b)(m) was in the range of 1-3 for Cu(II) depending on the applied Cu concentration. Two ternary complexes of DOM-OFL-Cu and DOM-Cu-OFL were proposed. For Mg(II), ΔC(b)/C(b)(m) was around -1 at Mg(II) concentrations lower than 1 mM, but decreased up to -5 with increasing Mg(II) concentration. The competitive effect of Mg(II) to OFL was thus proposed. FTIR spectra were collected for mechanistic discussion.