Structural Design of π-d Conjugated TMx B3 N3 S6 (x=2, 3) Monolayer Toward Electrocatalytic Ammonia Synthesis.

Single-atom catalysts (SACs) have attracted wide attention to be acted as potential electrocatalysts for nitrogen reduction reaction (NRR). However, the coordination environment of the single transition metal (TM) atoms is essential to the catalytic activity for NRR. Herein, we proposed four types of 3-, 4-coordinated and π-d conjugated TMx B3 N3 S6 (x=2, 3, TM=Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Tc, Ru, Hf, Ta, W, Re and Os) monolayers for SACs. Based on density functional theory (DFT) calculations, I-TM2 B3 N3 S6 and III-TM3 B3 N3 S6 are the reasonable 3-coordinated and 4-coordinated structures screening by structure stable optimizations, respectively. Next, the structural configurations, electronic properties and catalytic performances of 30 kinds of the 3-coordinated I-TM2 B3 N3 S6 and 4-coordinated III-TM3 B3 N3 S6 monolayers with different single transition metal atoms were systematically investigated. The results reveal that B3 N3 S6 ligand is an ideal support for TM atoms due to existence of strong TM-S bonds. The 3-coordinated I-V2 B3 N3 S6 is the best SAC with the low limiting potential (UL ) of -0.01 V, excellent stability (Ef =-0.32 eV, Udiss =0.02 V) and remarkable selectivity characteristics. This work not only provides novel π-d conjugated SACs, but also gives theoretical insights into their catalytic activities and offers reference for experimental synthesis.

3D hierarchically fractal structure stabilized anode for achieving long-term cycle life of aqueous Zn-ion batteries.

The cycling stability of aqueous Zn-ion battery (AZIB) is a serious issue for their successful application, mainly due to the considerable growth of Zn dendrites and the existence of side effects during operation. Herein, the hierarchically three-dimensional (3D) fractal structure of the ZnO/Zn/CuxO@Cu (ZZCC) anode is prepared by a two-step process, where CuxO nanowires are prepared on Cu foam by thermal oxidation method and Zn layer and ZnO surface are formed by plating. This fractal structure increases the electrodynamic surfaces and reduces the local current density, which can regulate Zn plating and inhibit dendritic growth and side effects. Apparently, the symmetric ZZCC-based cell shows a long-term operation time of 3000 h at 1 mA cm-2 with 1 mAh cm-2, and an operation time of more than 1000 h with a discharge depth of 15.94%. Compared with the bare Zn foil anode, the AZIB assembled with the composite of Mn-doped vanadium oxide and reduced graphene oxide cathode and ZZCC anode (MnVO@rGO//ZZCC) exhibits significantly improved cyclability (i.e. with 88.5% capacity retention) and achieves a Coulomb efficiency of 99.4% at 2 A g-1. This hierarchically 3D structure strategy to design anodes with superior cyclic stability contributes to the next generation of secure energy.

The novel π-d conjugated TM2B3N3S6 (TM = Mo, Ti and W) monolayers as highly active single-atom catalysts for electrocatalytic synthesis of ammonia.

Recently, single-atom catalysts (SACs) are receiving significant attention in electrocatalysis fields due to their excellent specific activities and extremely high atomic utilization ratio. Effective loading of metal atoms and high stability of SACs increase the number of exposed active sites, thus significantly improving their catalytic efficiency. Herein, we proposed a series (29 in total) of two-dimensional (2D) conjugated structures of TM2B3N3S6 (TM means those 3d to 5d transition metals) and studied the performance as single-atom catalysts for nitrogen reduction reaction (NRR) using density functional theory (DFT). Results show that TM2B3N3S6 (TM = Mo, Ti and W) monolayers have superior performance for ammonia synthesis with low limiting potentials of -0.38, -0.53 and -0.68 V, respectively. Among them, the Mo2B3N3S6 monolayer shows the best catalytic performance of NRR. Meanwhile, the π conjugated B3N3S6 rings undergo coordinated electron transfer with the d orbitals of TM to exhibit good chargeability, and these TM2B3N3S6 monolayers activate isolated N2 according to the "acceptance-donation" mechanism. We have also verified the good stability (i.e., Ef < 0, and Udiss > 0) and high selectivity (Ud = -0.03, 0.01 and 0.10 V, respectively) of the above four types of monolayers for NRR over hydrogen evolution reaction (HER). The NRR activities have been clarified by multiple-level descriptors (ΔG*N2H, ICOHP, and Ɛd) in the terms of basic characteristics, electronic property, and energy. Moreover, the aqueous solution can promote the NRR process, leading to the reduction of ΔGPDS from 0.38 eV to 0.27 eV for the Mo2B3N3S6 monolayer. However, the TM2B3N3S6 (TM = Mo, Ti and W) also showed excellent stability in aqueous phase. This study proves that the π-d conjugated monolayers of TM2B3N3S6 (TM = Mo, Ti and W) as electrocatalysts show great potentials for the nitrogen reduction.

Climatic factors and human disturbance influence ungulate species distribution on the Qinghai-Tibet Plateau.

Due to human activities and climate change, the habitats of ungulate species on the Qinghai-Tibet Plateau have been greatly affected in recent decades. In this study, the distribution patterns of 19 ungulate species on the Qinghai-Tibet Plateau were identified based on MaxEnt model in the past (1960-1990) and current periods (2000-2015). Then the changes of their habitat distribution and the species richness in different periods were compared. Finally, the Zonation model was used to identify the key protected areas of ungulate species. The results show that the MaxEnt model can well predict the distribution of ungulate species. Most ungulate species are mainly distributed in the southeast of the Qinghai-Tibet Plateau. The distance to lakes and precipitation are the main factors affecting the distribution of most ungulate species. The habitats originally located in the southeast of the Qinghai-Tibet Plateau have mainly extended northeastwards, while the habitats originally located in the northwest has been largely lost. The changes in the habitats of ungulate species in the southeast and northwest are diametrically opposite. The key protected areas identified by Zonation model are mainly located in the southeast of the Qinghai-Tibet Plateau. The existing nature reserves can effectively protect the suitable habitats of the Tibetan antelope, Tibetan wild ass and wild yak. This research can provide scientific basis for coordinating the contradiction between development and protection and promoting the biodiversity conservation on the Qinghai-Tibet Plateau.

Identification of key priority areas under different ecological restoration scenarios on the Qinghai-Tibet Plateau.

With the intensification of climate warming and human activities, the ecosystems on the Qinghai-Tibet Plateau (QTP) are facing increasing threats which leads to extensive ecological degradation. Ecological restoration measures need to be implemented to improve biodiversity and ecosystem services to mitigate the impact of climate change and human disturbances. However, the key priority areas (KPAs) for ecological restoration are not clear on the QTP, and the benefits of ecosystem services for ecological restoration are often ignored. In this study, we are the first to identify the KPAs based on the quantitative evaluation method and multicriteria optimization algorithm under five restoration scenarios aiming at ecosystem service improvement on the QTP. Results showed that: (1) The benefits of ecological restoration for climate change mitigation and associated costs under different scenarios showed generally similar spatial variability, exhibiting higher in the south and lower in the west, which were different from those for biodiversity. (2) The restoration priorities in Sichuan and Yunnan were generally higher under scenarios Ⅱ and Ⅴ, while in Xinjiang, Sichuan, Yunnan, and western and southern Tibet were higher under scenarios Ⅰ, Ⅲ and Ⅳ. (3) For different ecosystems, the similarities lied in that the restoration priorities of wetland ecosystem were the highest, while those of desert ecosystem were the lowest under five restoration scenarios. (4) When the restoration area requirement was 25% of the total degraded area, the highest restoration priority levels under scenarios Ⅰ, Ⅲ and Ⅳ were mainly distributed in Guinan, Renbu, Nierong and Chayu counties, and under scenarios Ⅱ and Ⅴ were mainly distributed in Renbu, Lang and Guinan counties. When the restoration area requirements were 50% and 75% of the total degraded area, the counties with higher restoration priority levels under scenario Ⅱ were different from those under other four scenarios. This study identified the KPAs under different restoration scenarios, which provided references for the restoration measures implementation on the QTP.

Composition and Diversity of Soil Microbial Community Associated With Land Use Types in the Agro-Pastoral Area in the Upper Yellow River Basin.

The microorganisms of soil are sensitive to their living microenvironment, and their community structure and function will change with the environmental conditions. In the agro-pastoral area on the Qinghai-Tibet Plateau, revealing the diversity of the soil microbial communities and its response to different soil physicochemical properties and environmental factors are important for ecosystem management. The microbial (bacteria and archaea) community composition and diversity under different land use types (cultivated land, grazing grassland and planted forest) were analyzed by 16S rRNA (V4 region) method in a typical agro-pastoral region in the upper Yellow River basin. Also, the soil nutrients were studied and correlated with the microbial community. The results showed that the soil nutrient contents in grassland were low, but the available nutrients were relatively high. There was a great spatial variability under different distances to the river. The microbial community diversity was lower in the grassland than the cultivated land and forest land closer to the river. For all land uses, the dominant phyla of soil microorganisms included Proteobacteria, Actinobacteria, and Bacteroidetes, while the abundance of Clostridia was significantly higher than that of the other groups, indicating that Clostridia dominated the Firmicutes and affected soil microbial community composition. The linear discriminant analysis (LDA) effect size (LefSe) analysis showed different biomarkers were more abundant in grassland than other land use types, suggesting that the structure and diversity of soil microorganisms in grassland were significantly different compared with cultivated land and forest land. The distance-based redundancy analysis (db-RDA) results showed that the total phosphorus (TP) and calcium (Ca) were the key environmental factors affecting the diversity and abundance of the soil microbial community in cultivated land and forestland, respectively. However, the microbial diversity in grassland was more related to spatial distance of the river. These results provided a theoretical basis for the changes in the composition, structure, and function of soil microbial communities in agro-pastoral areas.

MnCo2O4/Ni3S4 nanocomposite for hybrid supercapacitor with superior energy density and long-term cycling stability.

MnCo2O4 is regarded as a good electrode material for supercapacitor due to its high specific capacity and good structural stability. However, its poor electrical conductivity limits its wide-range applications. To solve this issue, we integrated the MnCo2O4 with Ni3S4, which has a good electrical conductivity, and synthesized a MnCo2O4/Ni3S4 nanocomposite using a two-step hydrothermal process. Comparing with individual MnCo2O4 and Ni3S4, the MnCo2O4/Ni3S4 nanocomposite showed a higher specific capacity and a better cycling stability as the electrode for the supercapacitor. The specific capacity value of the MnCo2O4/Ni3S4 electrode was 904.7 C g-1 at 1 A g-1 with a potential window of 0-0.55 V. A hybrid supercapacitor (HSC), assembled using MnCo2O4/Ni3S4 and active carbon as the cathode and anode, respectively, showed a capacitance of 116.4 F g-1 at 1 A g-1, and a high energy density of 50.7 Wh kg-1 at 405.8 W kg-1. Long-term electrochemical stability tests showed an obvious increase of the HSC's capacitance after 5500 charge/discharge cycles, reached a maximum value of ∼162.7% of its initial value after 25,000 cycles, and then remained a stable value up to 64,000 cycles. Simultaneously, its energy density was increased to 54.2 Wh kg-1 at 380.3 W kg-1 after 64,000 cycles.

Effects of the interaction among climate, terrain and human activities on biodiversity on the Qinghai-Tibet Plateau.

Disentangling the driving factors of biodiversity is critical for understanding biogeographical patterns of vegetation and ecosystem function. However, the biotic and abiotic attributes that shape biodiversity on the Qinghai-Tibet Plateau (QTP) are still not been quantified. Previous studies have not distinguished the direct and indirect effects of climate, terrain, and human disturbance on biodiversity. In this study, we applied a structural equation model (SEM) to assess the interactions among 4 attributes and biodiversity. A conceptual framework with 8 explanatory variables was built to identify the driving forces of biodiversity. A geographically weighted regression (GWR) model was applied to explore the response sensitivity of biodiversity to climate, terrain, and human attributes. We found that the SEM passed the tests of validity, reliability and fit, indicating that the hypothetical model was reasonable and credible. Among terrain conditions, elevation had the greatest, most-negative effect on biodiversity. Among the human factors, distance to town showed the strongest and most negative influence on biodiversity. Among the climate factors, precipitation had the greatest influence on biodiversity. Moreover, the direct effects of terrain and human activity were 0.348 and 0.135, respectively, and their indirect effects were 0.769 and 0.213, respectively, revealing that they had stronger indirect effects on biodiversity than direct effects. Climate exhibited only direct effects on biodiversity and had no indirect effects. The total effects of climate, terrain and human activity on biodiversity were 1.39, 0.35 and 0.13, respectively, indicating that climate was the main driving force of biodiversity on the QTP. The response sensitivity of biodiversity to climate, terrain and human factors showed obvious spatial variations. This study contributes to exploring the interactive effects and driving mechanisms of human-natural attributes on biodiversity and provides further effective guidance and support for biodiversity conservation and restoration.

Long-term dynamics of nitrogen flow in a typical agricultural and pastoral region on the Qinghai-Tibet Plateau and its optimization strategy.

Nitrogen (N) plays a central role in livestock development and food production in agricultural and pastoral regions, while its flow and loss can affect environmental quality, biodiversity and human health. A comprehensive understanding of the sources, patterns and drivers of N flow helps to alleviate its negative effects and promote sustainable management. We developed a county-scale N flow model to quantitatively analyze the N use efficiency (NUE), N losses and their driving forces in the food production and consumption system (FCPS) on the Qinghai-Tibet Plateau (QTP). More sustainable N utilization was further investigated through scenario analyses. Our results revealed that N fluxes doubled from 1998 to 2018 to maintain the growing demands for human food production and consumption in Ledu County, which was related to the increasing N losses to the atmosphere and water environment. The surging N fluxes greatly changed the N distribution pattern, resulting in a relatively low NUE (mean value: 29.41%) in the crop-production subsystem (CPS) and a relatively high NUE (mean value: 23.50%) in the livestock-breeding subsystem (LBS). The CPS contributed the most to the N losses. The urban population, animal-derived consumption, crop planting structure, imported fodder and N fertilizer application level were closely associated with N losses. The scenario analysis indicated that combined reasonable changes in planting structure, precision animal feeding, fertilizer management, diets and conversion of cropland into pasture could reduce N losses in 2030 to 5%-61% of Business as usual level. Our results highlighted the strong anthropogenic impact on the N flow of food production and consumption and suggested a sustainable N flow management strategy to harmonize the relationship between N flow and anthropogenically driven factors on the QTP.

The cost-benefit evaluation based on ecosystem services under different ecological restoration scenarios.

The effects of ecological restoration based on ecosystem services (ES) have attracted more and more attention, while the simulation and cost-benefit analysis of ecological restoration scenarios are not well investigated. In this study, four ecological restoration scenarios were simulated at a typical watershed on the Qinghai-Tibetan Plateau (QTP) based on the land use conversion. Scenario 1 was only grassland restoration, Scenario 2 and 3 were mainly farmland to shrub, and Scenario 4 was mainly grassland restoration with bare land converting to forest and shrub. The ecosystem services value (ESV) and the cost-benefits of these scenarios were quantified and compared in 25 years after the restoration investment. The results showed there were significant differences in the ESV under four scenarios, among which Scenario 4 had the largest ESV and Scenario 1 had the smallest ESV. The spatial distribution of ESV was uneven, and high-value regions were concentrated in the southwest and central regions. There were great variations between original scenario and simulated scenarios, but a little difference between Scenarios 2, 3, and 4. The largest loss of farmland abandonment was regulating service, followed by supporting service, provisioning service, and cultural service. From the perspective of payback period, Scenario 1 was the fastest, and it could obtain net benefits first. From the short- and long-term (6 and 25 years after investment) benefits, Scenarios 1 and 4 had the largest cumulative ESV increase, respectively. The results of this study can provide a basis for the formulation and implementation of ecological policies.

Spatial differentiation of the NPP and NDVI and its influencing factors vary with grassland type on the Qinghai-Tibet Plateau.

Grasslands are the dominant ecosystem of the Qinghai-Tibet Plateau (QTP), and they play an important role in climate regulation and represent an important ecological barrier in China. However, the spatial differentiation characteristics of net primary productivity (NPP) and normalized differential vegetation index (NDVI) and the main influencing factors that vary with grassland type on the QTP are not clear. In this study, standardized precipitation evapotranspiration index (SPEI), digital elevation model (DEM), precipitation, temperature, slope, photosynthetically active radiation (PAR) and grazing intensity were considered the driving factors. First, a grey relational degree analysis was performed to test for the quantitative relationships between NPP, NDVI and factors. Then, the geographical detector method was applied to analyze the interaction relationships of the factors. Finally, based on the geographically weighted regression (GWR) model, the influence of factors varied with grassland type on the NPP and NDVI was revealed from the perspective of spatial differentiation. The results were as follows: (1) The NPP and NDVI had roughly the same degrees of correlation with each impact factor by the grey relational degree analysis, each factor was closely related to the NPP and NDVI, and the relational degree between grazing intensity and NPP was greater than that between grazing intensity and NDVI. (2) The interaction relationships between influencing factors and NPP and NDVI varied with the grassland type and presented bivariate enhancement and nonlinear enhancement, and the interaction effects between grazing intensity and any factor on each grassland type had a greater impact on NPP. (3) The main influencing factors of the spatial heterogeneity of NPP were grazing intensity and PAR, which were "high from northeast to southwest, low from northwest to southeast" and "low in the middle and high around". The main influencing factors on the NDVI were precipitation and PAR, which were "low in the middle and high around" and "high in the north, low in the south".

Air pollution and cause-specific mortality: A comparative study of urban and rural areas in China.

Air pollution increases the risks of all-cause mortality, cardiovascular mortality and respiratory mortality across China. However, the urban-rural differences in the associations between air pollution and mortality have not been clearly identified. In this study, a distributed lag nonlinear model was used to examine whether the air pollutants-mortality associations vary between urban and rural areas. Then, we used logistic regression analyses to evaluate the air pollutants-mortality relations. Also, generalized additive models were simulated to evaluate the nonlinear curves. Our results showed that the relative risks of air pollution-related mortality were generally higher in rural areas, where PM2.5 pollution was the dominant factor (p-value < 0.05). Mortality risks for all-cause, cardiovascular and respiratory will increase when average annual PM2.5 concentrations exceed approximately 38 µg/m3, 41 µg/m3 and 41 µg/m3, respectively, all of which exceed the annual Grade II standards. In urban areas, PM10-2.5 and NO2 were associated with mortality (p-value < 0.05). We proposed some area-specific strategies for controlling the NO2 pollution and PM10-2.5 pollution in urban areas and the PM2.5 pollution in rural areas to eliminate the gaps. Our findings identify that rural residents are more sensitive to air pollution than urban residents in China, and this result challenges previous assumptions about the more adverse effects of urbanization on residents' health in developing countries.

Assessing NO2-related health effects by non-linear and linear methods on a national level.

Exposure to NO2 pollution has a significant adverse effect on residents' health. However, few studies have assessed the health effects associated with NO2 pollution. Compared with PM2.5 pollution, the harmfulness of NO2 pollution has not been quantitatively studied or clearly identified. In this study, we assessed the NO2 exposure-related health effects by non-linear and linear methods, taking advantage of online monitoring and survey data. We also assessed the economic cost of NO2 pollution in 338 cities in China. Our results showed that the average annual concentration of NO2 in the top fifteen cities with more than ten million permanent residents (except for Shenzhen, in the Guangdong province) exceeded the annual Grade II standards (40 µg/m3). The estimated national NO2-related all-cause mortality for non-linear and linear methods were 388.5 × 103 (95% CI: 198.1 × 103-748.2 × 103) and 374.1 × 103 (95% CI: 194.3 × 103-695.9 × 103), respectively. The total calculated national economic cost was about 28.8 billion US$ (95% CI: 14.7-55.4) in 2016. In addition, the comparison results showed that the harm caused by PM2.5 pollution was about four times that of NO2 pollution. Our statistics contribute to the limited research on NO2 pollution's effects on health and the economy in China.

Electronic Modulation of Nickel Disulfide toward Efficient Water Electrolysis.

Developing highly efficient earth-abundant nickel-based compounds is an important step to realize hydrogen generation from water. Herein, the electronic modulation of the semiconducting NiS2 by cation doping for advanced water electrolysis is reported. Both theoretical calculations and temperature-dependent resistivity measurements indicate the semiconductor-to-conductor transition of NiS2 after Cu incorporation. Further calculations also suggest the advantages of Cu dopant to cathodic water electrolysis by bringing Gibbs free energy of H adsorption at both Ni sites and S sites much closer to zero. It is noteworthy that water dissociation on Cu-doped NiS2 (Cu-NiS2 ) surface is even more favorable than those on NiS2 and Pt(111). Thus, the prepared Cu-NiS2 shows noticeably improved performance toward alkaline hydrogen and oxygen evolution reactions (HER and OER). Specifically, it requires merely 232 mV OER overpotential to drive 10 mA cm-2 ; in parallel with Tafel slopes of 46 mV dec-1 . Regarding HER, an onset overpotential of only 68 mV is achieved. When integrated as both electrodes for water electrolysis, Cu-NiS2 needs only 1.64 V to drive 10 mA cm-2 , surpassing the state-of-the-art Ir/C-Pt/C couple (1.71 V). This work opens up an avenue to engineer low-cost and earth-abundant catalysts performing on par with the noble-metal-based one for water splitting.

The spatio-temporal patterns of the topsoil organic carbon density and its influencing factors based on different estimation models in the grassland of Qinghai-Tibet Plateau.

The grassland soils of the Qinghai-Tibet Plateau (QTP) store a large amount of organic carbon because of the cold, humid climate, and topsoil organic carbon is quite sensitive to global climate changes. However, the spatio-temporal dynamics and factors that influence the soil organic carbon (SOC) on the QTP's grassland are not understood well. Moreover, there are few comparative analyses of different approaches to estimate the QTP' SOC. In this study, we estimated the storage and patterns of SOC density (SOCD) using several methods, including MODIS (moderate-resolution imaging spectroradiometer) retrieval, field data and previous empirical models (Models1-4, and soil organic matter (SOM)). And their relations with aboveground biomass, soil moisture, temperature, elevation, and soil conductivity were further explored. The results showed that SOC showed a similar variation trend in the different models, in which it decreased with increasing bulk density (BD) in the topsoil at 30 cm. For meadow and steppe grasslands, Models 1, 2, and 4 showed similar estimated values of SOCD, while Model3 had a lower value than them. SOC storage in the BD 3 and SOM methods had abnormal values, while the MODIS-NDVI, BD 1, 2, and 4 methods had similar SOC stock values for meadow and steppe grassland. Moreover, meadow grassland had a higher SOC storage than did steppe grassland, with means values of 397.9×1010 kg and 242.2×1010 kg, respectively. SOCD's spatial distribution using MODIS-NDVI method differed clearly from the empirical models, with a significant tendency for spatial variation that increased from the northwestern to southeastern regions on the QTP. Therefore, based on the values estimated and spatial variation features, the MODIS-NDVI method may be a more feasible and valid model to estimate SOC. Moreover, the mean annual SOCD values during 2000-2015 showed an increasing trend, with a higher mean value in meadow and a lower mean value in steppe. Further, SOCD was correlated significantly and positively with aboveground biomass and soil moisture, and negatively correlated with elevation and soil conductivity. Increasing temperature had negative effects on SOCD, which was consistent with the global trend. These results indicated that topsoil moisture plays a key role in SOCD spatial patterns. Our results provide valuable support for the long-term estimation of SOCD in future research on the QTP.

The alpine meadow around the mining areas on the Qinghai-Tibetan Plateau will degenerate as a result of the change of dominant species under the disturbance of open-pit mining.

Mining is well-known as one of the most aggressive human disturbances leading to massive and irreversible damages to natural ecosystems. However, the influence mechanisms of open-pit mining on plant communities and soil properties of alpine meadow on the Qinghai-Tibetan plateau are not well understood. In this study, we used structural equation modeling (SEM) to study the influence mechanisms in the disturbed areas of the Qulong copper mine. Our results revealed that the soil parameters of alpine meadow have been significantly changed by mining activities. SEM results showed that Plantago depressa Willd. was more suitable for growing in current soil conditions due to its tolerance to heavy metals than other dominant species, which meant that it would substitute the current two dominant species (Kobresia myosuroides (Villars) Fiori and Blysmus sinocompressus Tang et Wang) in the future and become the most important dominant species in the study area. Unfortunately, the Shannon-Wiener index, Alatalo evenness index and M-Gordon stability index are relatively low in the plot with Plantago depressa Willd. as the dominant species. In a word, the fragile alpine meadow ecosystem may degenerate in the future due to plants and soil disturbed by mining activities. Further, eight targeted recommendations were proposed to protect alpine meadow on the Qinghai-Tibetan plateau.

Spatio-temporal evolution scenarios and the coupling analysis of ecosystem services with land use change in China.

Ecosystem service (ES) supply and demand are affected by changes in land use and the supply of specific ecosystem services for human consumption, respectively. Future spatio-temporal dynamics and their coupling relations with land use in China have not been well analysed. In this study, based on future land use scenarios of Li's database, ES supply, demand and balance (supply minus demand) were revealed utilizing land use and land cover (LULC) matrix model in China in 2010, 2050 and 2100. The results showed that ES supply, demand and balance had great spatial and temporal variations under different scenarios at national and provincial scales. Higher population and higher urban expansion scenarios will lead to a significant decreasing in the balance values of different categories and total ESs in most provinces. The ecological sensitivity index was calculated to indicate the impact of land use intensity on ecosystem services. The results showed that the sensitivity levels in approximately 90% of provinces were low for all the scenarios, as only Anhui, Zhejiang, Jiangxi and Liaoning in 2050 and Gansu in 2100 were extremely sensitive to changes in supply, while only provinces in the central-eastern regions were sensitive with obvious differences from the demand. The coupling coordination analysis between land use intensity and ES balance was applied to identify the provinces with low-level coordination in land use and ES management. The results showed that the coordination change in most provinces remained stable under four scenarios. However, some provinces displayed an improving trend from low to moderate coordination or from moderate to high coordination and a degrading trend from moderate to low coordination or from high to moderate coordination from 2010 to 2100. This study contributes to exploring the effect of land use on ecosystem service evolution, thereby providing credible guidance for future land and ES management.

Identifying the contributions of multiple driving forces to PM10-2.5 pollution in urban areas in China.

Economic development and urban expansion have accelerated particulate matter pollution in urban areas in China. Particulate matter-driven haze poses a serious threat to human beings from a public health point of view. Substantial evidences had linked adverse health effects with exposures to PM2.5, but recent research indicated that PM10-2.5 also had great risk. However, the relative contributions of driving forces to PM10-2.5 pollution are not well understood in the urban areas in China, and no targeted policies have been regulated to control the pollution. In this study, we quantified the contributions of potential driving factor across China with the structural equation model (SEM). Our results showed that in 2015 and 2016, the annual average concentrations of PM10-2.5 in the 290 prefecture-level cities with a mean value of 36 and 35 µg/m3, respectively. Industrial scale contributed more to PM10-2.5 pollution than city size and residents' activities in urban areas based on SEM results. Driving forces included in our model could explain 42% of variations in PM10-2.5 pollution, which indicated that there existed influences from other anthropogenic sources and natural sources. Eleven targeted recommendations were then proposed to control PM10-2.5 pollution based on our mechanism analysis. Findings from our study are beneficial to control PM10-2.5 pollution on a national scale, and also can provide a theoretical basis for the formulation of PM10-2.5 pollution control policy in China.

Transition metal atom (Ti, V, Mn, Fe, and Co) anchored silicene for hydrogen evolution reaction.

Non-noble element catalysis for hydrogen evolution reaction (HER) is a promising pathway for mass hydrogen production through electrochemical water splitting. In this work, the catalytic performance of metal (alkali, alkali-earth, and transition metal) atoms anchored to silicene was investigated by density functional theory. Results showed that all the studied metal atoms are energetically favorably absorbed on the silicene with large binding energies. The pristine silicene is catalytically inert for HER, while the metal (Fe, V, Mn, Ti, Co, Ni, Be, and Cr) atom anchored silicene is catalytically active for HER with the calculated Gibbs free energies in the range between -0.09 and 0.18 eV, which is very close to the optimum value of 0.0 eV. These results suggested that the catalytic behavior of silicene can be effectively improved by metal adsorption. Such metal (Fe, V, Mn, Ti, Co, Ni, Be, and Cr) atom anchored silicenes can be used as potential catalysts for HER.