Emissions of HCFC-22 and HCFC-142b in China during 2018-2021 Inferred from Inverse Modeling.

Hydrochlorofluorocarbons (HCFCs) are transitional substitutes for chlorofluorocarbons (CFCs). However, they still have the capacity to be ozone-depleting substances (ODSs). Therefore, they are scheduled to be phased out in China by 2030 under the Montreal Protocol. The emission estimates of HCFC-22 (CHClF2) and HCFC-142b (CH3CClF2) in China using atmospheric observations are lacking after 2017, making it hard to understand the effectiveness of the phase-out process of HCFCs in China. Here, we use flask and in situ measurements of HCFC-22 and HCFC-142b during 2018-2021 and inverse modeling to determine the emission magnitude and changes in China. It was determined that China's emissions were 172 ± 40, 154 ± 39, 160 ± 22, and 155 ± 33 Gg yr-1 of HCFC-22 and 8.3 ± 1.8, 7.8 ± 1.6, 7.4 ± 1.7, and 7.9 ± 1.7 Gg yr-1 of HCFC-142b from 2018 to 2021, respectively. Top-down estimates show that HCFC-22 emissions in China were stable, while HCFC-142b emissions were decreasing during 2013-2021, although both substances were in the stage of being phased out during 2013-2021. This study reveals that 46 and 39% of the global HCFC-22 and HCFC-142b emissions, respectively, cannot be traced to certain countries in 2020. We suggest that more studies on HCFC emissions around the world in the future are needed to better safeguard the ozone layer recovery and climate mitigation by ensuring compliance with the Montreal Protocol during HCFC phase-out processes.

Estimate Gaps of Montreal Protocol-Regulated Potent Greenhouse Gas HFC-152a Emissions in China Have Been Explained.

1,1-Difluoroethane (HFC-152a) is a hydrofluorocarbon regulated by the Montreal Protocol, and its emissions in China are of concern as China will regulate HFC-152a in 2024. However, no observation-inferred top-down estimates were undertaken after 2017, and substantial gaps existed among previous estimates of China's HFC-152a emissions. Using the atmospheric observations and inverse modeling, this study reveals China's HFC-152a emissions of 9.4 ± 1.7 Gg/yr (gigagrams per year), 10.6 ± 1.8 Gg/yr, and 9.7 ± 1.5 Gg/yr in 2018, 2019, and 2020, respectively. In addition, we display an overall increasing trend during 2011-2020, which is in contrast to the decreasing and steady trend reported by the Emission Database for Global Atmospheric Research (EDGAR) and the Chinese government, respectively. Subsequently, we establish a comprehensive bottom-up emission inventory matching with top-down estimates and thus succeed in explaining the gaps among previous estimates. Furthermore, the contribution of China's emissions to global HFC-152a emission growth increased from 15% during 2001-2010 to >100% during 2011-2020. An emission projection based on our improved inventory shows that the Kigali Amendment (KA) would assist in avoiding 1535.6-4710.6 Gg (251.8-772.5 Tg CO2-eq) HFC-152a emissions during 2024-2100. Our findings indicate relatively accurate China's HFC-152a emissions and provide scientific support for addressing climate change and implementing the KA.

Characteristics of China's coal mine methane emission sources at national and provincial levels.

Methane (CH4) is the second most abundant greenhouse gas. China is the largest CH4 emitter in the world, with coal mine methane (CMM) being one of the main anthropogenic contributions. Thus, there is an urgent need for comprehensive estimates and strategies for reducing CMM emissions in China. However, the development of effective strategies is currently challenged by a lack of information on temporal variations in the contributions of different CMM sources and the absence of provincial spatial analysis. Here, considering five sources and utilization, we build a comprehensive inventory of China's CMM emissions from 1980 to 2022 and quantify the contributions of individual sources to the overall CMM emissions at the national and provincial levels. Our results highlight a significant shift in the source contributions of CMM emissions, with the largest contributor, underground mining, decreasing from 89% in 1980 to 69% in 2022. Underground abandoned coal mines, which were ignored or underestimated in past inventories, have become the second source of CMM emissions since 1999. From 2011 to 2022, we identified Shanxi, Guizhou, and Shaanxi as the three largest CMM-emitting provinces, while the Emissions Database for Global Atmospheric Research (EDGAR) v8 overestimated emissions from Inner Mongolia, ranking it third. Notably, we observed a substantial decrease (exceeding 1 Mt) in CMM emissions in Sichuan, Henan, Liaoning, and Hunan between 2011 and 2022, which was not captured by EDGAR v8. To develop targeted CMM emission reduction strategies at the provincial level, we classified 31 provinces into four groups based on their CMM emission structures. In 2022, the number of provinces with CMM emissions mainly from abandoned coal mines has exceeded that of provinces with mainly underground mines, which requires attention. This study reveals the characteristics of the source of CMM emissions in China and provides emission reduction directions for four groups of provinces.

Inverse Modeling Revealed Reversed Trends in HCFC-141b Emissions for China during 2018-2020.

Having the highest ozone-depleting potential among hydrochlorofluorocarbons (HCFCs), the production and consumption of HCFC-141b (1,1-dichloro-1-fluoroethane, CH3CCl2F) are controlled by the Montreal Protocol. A renewed rise in global HCFC-141b emissions was found during 2017-2020; however, the latest changes in emissions across China are unclear for this period. This study used the FLEXible PARTicle dispersion model and the Bayesian framework to quantify HCFC-141b emissions based on atmospheric measurements from more sites across China than those used in previous studies. Results show that the estimated HCFC-141b emissions during 2018-2020 were on average 19.4 (17.3-21.6) Gg year-1, which was 3.9 (0.9-7.0) Gg year-1 higher than those in 2017 (15.5 [13.4-17.6] Gg year-1), showing a renewed rise. The proportion of global emissions that could not be exactly traced in 2020 was reduced from about 70% reported in previous studies to 46% herein. This study reconciled the global emission rise of 3.0 ± 1.2 Gg year-1 (emissions in 2020 - emissions in 2017): China's HCFC-141b emissions changed by 4.3 ± 4.5 Gg year-1, and the combined emissions from North Korea, South Korea, western Japan, Australia, northwestern Europe, and the United States changed by -2.2 ± 2.6 Gg year-1, while those from other countries/regions changed by 0.9 ± 5.3 Gg year-1.

Assessment on China's urbanization after the implementation of main functional areas planning.

China has implemented main functional areas planning (MFAP) since 2010, which is essential for improving the efficiency of land space utilization and achieving sustainable urban development. Quantitative assessments of the urban development levels (UDLs) at the county level across China after the implementation of MFAP have not been well-documented. In this study, a unified indicator system was developed, and the UDLs of 2850 counties in China after MFAP implementation were evaluated. The results showed that MFAP played a positive role in urban development in China. The UDLs in China generally increased but showed obvious spatial differences. The higher UDLs were mostly found in the counties in the five urban belts, which reflects the overall urban layout of China. The UDLs were generally low in the western counties in comparison with those in the eastern part of China. The differences in the UDLs from east to west were greater than those from north to south. Moreover, the differences in the UDLs presented a spatial agglomeration effect. This study could offer insight into the refinement of MFAP in China and sustainable urban development in developing countries.

Role of Acid in Tailoring Prussian Blue as Cathode for High-Performance Sodium-Ion Battery.

Prussian blue (PB) with concave centers is synthesized successfully through a hydrothermal method with the assistance of acid. In this study, the role of the acid is investigated systematically by adjusting the reaction temperature and time, using different kinds and amounts of acid, and changing the amount of PVP surfactant added. It is found that the acid can not only trigger the chemical reaction to form cubic PB, but also act as an etching reagent to tailor the morphology. The as-obtained cubic PB with concave centers demonstrates a superior cycle stability and rate performance, which can achieve a capacity of 107 mA h g-1 at 0.2 A g-1 . The corresponding capacity retention is 74 % after 500 cycles relative to the second cycle. Even at a current density of 5 A g-1 , the specific capacity remains at 82 mA h g-1 . Furthermore, the full cell, using PB as the cathode and hard carbon as the anode, exhibits a high capacity of 70 mA h g-1 at 0.1 A g-1 , and can power an LED light successfully. This work provides new insights into the role of acid in tailoring the morphology of PB, and opens a new avenue toward the design of unique structures to improve sodium storage.

Bio-Inspired Synthesis of an Ordered N/P Dual-Doped Porous Carbon and Application as an Anode for Sodium-Ion Batteries.

Carbonaceous materials are one of the most promising anode materials for sodium-ion batteries, because of their abundance, stability, and safe usage. However, the practical application of carbon materials is hindered by poor specific capacity and low initial Coulombic efficiency. The design of porous structure and doping with heteroatoms are two simple and effective methods to promote the sodium storage performance. Herein, the N, P co-doped porous carbon materials are fabricated using renewable and biodegradable gelatin as carbon and nitrogen resource, phosphoric acid as phosphorus precursor and polystyrene nanospheres as a template. The product can deliver a reversible capacity of 230 mA h g-1 at a current density of 0.2 A g-1 , and even a high capacity of 113 mA h g-1 at 10 Ag-1 . The enhanced sodium storage performance is attributed to the synergistic effect of the porosity and the dual-doping of nitrogen and phosphorus.

CCl4 emissions in eastern China during 2021-2022 and exploration of potential new sources.

According to the Montreal Protocol, the production and consumption of ozone-layer-depleting CCl4 for dispersive applications was globally phased out by 2010, including China. However, continued CCl4 emissions were disclosed, with the latest CCl4 emissions unknown in eastern China. In the current study, based on the atmospheric measurements of ~12,000 air samples taken at two sites in eastern China, the 2021-2022 CCl4 emissions are quantified as 7.6 ± 1.7 gigagrams per year. This finding indicates that CCl4 emissions continued after being phased out for dispersive uses in 2010. Subsequently, our study identifies potential industrial sources (manufacture of general purpose machinery and manufacture of raw chemical materials, and chemical products) of CCl4 emissions.

Nickel-Ion Activating Discarded COVID-19 Medical Surgical Masks for Forming Carbon-Nickel Composite Nanowires and Using as a High-Performance Lithium Battery Anode.

With the prevalence of COVID-19, wearing medical surgical masks has become a requisite measure to protect against the invasion of the virus. Therefore, a huge amount of discarded medical surgical masks will be produced, which will become a potential hazard to pollute the environment and endanger the health of organisms without our awareness. Herein, a green and cost-effective way for the reasonable disposal of waste masks becomes necessary. In this work, we realized the transformation from waste medical surgical masks into high-quality carbon-nickel composite nanowires, which not only benefit the protection of the environment and ecosystem but also contribute to the realization of economic value. The obtained composite carbon-based materials demonstrate 70 S m-1 conductivity, 5.2 nm average pore diameters, 234 m2 g-1 surface areas, and proper graphitization degree. As an anode material for lithium-ion batteries, the prepared carbon composite materials demonstrate a specific capacity of 420 mA h g-1 after 800 cycles at a current density of 0.2 A g-1. It also displays good rate performance and decent cycling stability. Therefore, this study provides an approach to converting the discarded medical surgical masks into high-quality carbon nanowire anode materials to turn waste into treasure.

Reductive Cross-Coupling of Aldehydes and Imines Mediated by Visible Light Photoredox Catalysis.

Under photoredox catalysis conditions, the conventional electrophilic reactivity of ketimines is inverted to generate nucleophilic species. As a result, chemoselective cross-electrophile couplings between aldehydes and ketimines are achieved via umpolung reactivity of ketimines to furnish amino alcohols (44 examples with good to excellent yields). To illustrate the utility of the amino alcohol products, 1,2-dihydroindol-3-one-based fluorophores are easily synthesized using the coupling products. Finally, a plausible reaction pathway is discussed.

Improved High Temperature Performance of a Spinel LiNi0.5Mn1.5O4 Cathode for High-Voltage Lithium-Ion Batteries by Surface Modification of a Flexible Conductive Nanolayer.

The composite cathode material of the conductive polymer polyaniline (PANI)-coated spinel structural LiNi0.5Mn1.5O4 (LNMO) for high-voltage lithium-ion batteries has been successfully synthesized by an in situ chemical oxidation polymerization method. The electrode of the LNMO-PANI composite material shows superior rate capability and excellent cycling stability. A capacity of 123.4 mAh g-1 with the capacity retention of 99.7% can be maintained at 0.5C after 200 cycles in the voltage range of 3.0-4.95 V (vs Li/Li+) at room temperature. Even with cycling at 5C, a capacity of 65.5 mAh g-1 can still be achieved. The PANI coating layer can not only reduce the dissolution of Ni and Mn from the LNMO cubic framework into the electrolyte during cycling, but also significantly improve the undesirable interfacial reactions between the cathode and electrolyte, and markedly increase the electrical conductivity of the electrode. At 55 °C, the LNMO-PANI composite material exhibits more superior cyclic performance than pristine, that is, the capacity retention of 94.5% at 0.5C after 100 cycles vs that of 13.0%. This study offers an effective strategy for suppressing the decomposition of an electrolyte under the highly oxidizing (>4.5 V) and elevated temperature conditions.

Visible light-promoted CO2 fixation with imines to synthesize diaryl α-amino acids.

Light-mediated transformations with CO2 have recently attracted great attention, with the focus on CO2 incorporation into C-C double and triple bonds, organohalides and amines. Herein is demonstrated visible light -mediated umpolung imine reactivity capable of engaging CO2 to afford α-amino acid derivatives. By employing benzophenone ketimine derivatives, CO2 fixation by hydrocarboxylation of C=N double bonds is achieved. Good to excellent yields of a broad range of α,α-disubstituted α-amino acid derivatives are obtained under mild conditions (rt, atmospheric pressure of CO2, visible light). A procedure that avoids tedious chromatographic purification and uses sustainable sunlight is developed to highlight the simplicity of this method.

Visible-Light-Mediated Umpolung Reactivity of Imines: Ketimine Reductions with Cy2NMe and Water.

A novel carbanionic reactivity of imines mediated by photoredox catalysis is demonstrated. The umpolung imine reactivity is exemplified by proton abstraction from water as a key step in the reduction of benzophenone ketimines to amines (up to 98% yield). Deuterium is introduced into amines efficiently using D2O as an inexpensive deuterium source (≥95% D ratio). The mechanism of this unusual transformation is probed.