Effect of carbonization atmosphere on electrochemical properties of nitrogen-doped porous carbon

Nitrogen atom doping has been found to enhance the electrochemical performance of porous carbon(PC).In this study,hollow tubular nitrogen-doped porous carbon(N/PC)was synthesized using polyvinylpyrrolidone as the carbon–nitrogen source and fibrous brucite as the template through carbonization.The effects of nitrogen and argon protective atmospheres on the nitrogen content,the specific surface area(SSA),and electrochemical properties of N/PC were investigated.The results showed that compared with N/FBC-Ar,N/FBC-N2 prepared in nitrogen protective atmosphere had a higher nitrogen content and a larger proportion of pyrrolic nitrogen(N-5)and pyridinic nitrogen(N-6).N/FBC-N2 displayed a specific capacitance(C)of 194.1 F·g^(−1)at 1 A·g^(−1),greater than that of N/FBC-Ar(174.3 F·g^(−1)).This work reveals that the nitrogen doping with a higher nitrogen content in nitrogen protective atmosphere is more favorable.Furthermore,a larger proportion of pyrrolic nitrogen and pyridinic nitrogen in the doped nitrogen atoms significantly enhances the electrochemical performance.

Carbonation of Dicalcium Silicate Enhanced by Ammonia Bicarbonate and Its Mechanism

The strength development law of γ-type dicalcium silicate (γ-C_(2)S) under different carbonation processes was investigated,and the carbonation mechanism of γ-C_(2)S under the action of NH_(4)HCO_(3) was clarified by using a wide range of test methods,including XRD and SEM.A method of saturated NH_(4)HCO_(3) solution as a curing agent was identified to improve the carbonation efficiency and enhance the carbonation degree of γ-C_(2)S,and then a high-strength carbonated specimen was obtained.Microhardness analysis and SEM morphology analysis were conducted on the carbonised specimens obtained under atmospheric pressure carbonisation conditions using the curing agent.It was found that γ-C_(2)S could perform carbonisation well under atmospheric pressure,which promoted the carbonisation efficiency and decreased the carbonisation cost simultaneously.Therefore,a new carbonisation process solution was proposed for the rapid carbonisation of γ-C_(2)S.

Spatiotemporal Characteristics of Atmospheric Brown Carbon Emis-sion from Combustion Sources in China

Atmospheric Brown Carbon(BrC)with strong wavelength-dependence light-absorption ability can significantly affect radiat-ive forcing.Highly resolved emission inventories with lower uncertainties are important premise and essential in scientifically evaluat-ing impacts of emissions on air quality,human health and climate change.This study developed a bottom-up inventory of primary BrC from combustion sources in China from 1960 to 2016 with a spatial resolution at 0.1°×0.1,based on compiled emission factors and detailed activity data.The primary BrC emission in China was about 593 Gg(500-735 Gg as interquartile range)in 2016,contributing to 7%(5%-8%)of a previously estimated global total BrC emission.Residential fuel combustion was the largest source of primary BrC in China,with the contribution of 67%as the national average but ranging from 25%to 99%among different provincial regions.Signi-ficant spatial disparities were also observed in the relative shares of different fuel types.Coal combustion contribution varied from 8%to 99%across different regions.Heilongjiang and North China Plain had high emissions of primary BrC.Generally,on the national scale,spatial distribution of BrC emission density per area was aligned with the population distribution.Primary BrC emission from combus-tion sources in China have been declined since a peak of~1300 Gg in 1980,but the temporal trends were distinct in different sectors.The high-resolution inventory developed here enables radiative forcing simulations in future atmospheric models so as to promote bet-ter understanding of carbonaceous aerosol impacts in the Earth's climate system and to develop strategies achieving co-benefits of hu-man health protection and climate change.

Response of atmospheric carbon dioxide to the secular variation of weakening geomagnetic field in whole atmosphere simulations

Responses of atmospheric carbon dioxide(CO_(2))density to geomagnetic secular variation are investigated using the Whole Atmosphere Community Climate Model-eXtended(WACCM-X).Our ensemble simulations show that CO_(2) volume mixing ratios(VMRs)increase at high latitudes and decrease at mid and low latitudes by several ppmv in response to a 50%weakening of the geomagnetic field.Statistically significant changes in CO_(2) are mainly found above~90 km altitude and primarily redetermine the energy budget at~100-110 km.Our analysis of transformed Eulerian mean(TEM)circulation found that CO_(2) change is caused by enhanced upwelling at high latitudes and downwelling at mid and low latitudes as a result of increased Joule heating.We further analyzed the atmospheric CO_(2) response to realistic geomagnetic weakening between 1978 and 2013,and found increasing(decreasing)CO_(2) VMRs at high latitudes(mid and low latitudes)accordingly.For the first time,our simulation results demonstrate that the impact of geomagnetic variation on atmospheric CO_(2) distribution is noticeable on a time scale of decades.

Analysis of the carbon dioxide mole fraction variation and its transmission characteristics in Taiyuan

Based on the concentrations of CO2,PM2.5 and PM1.0,and conventional meteorological observation data from 2016 to 2018 at Taiyuan station,which belongs to the Shanxi greenhouse gas observation network,the CO2 concentration monthly and daily distribution characteristics,the weekend effect,and the variation characteristics on haze days and non-haze days,are analyzed.By using the Hybrid Single-Particle Lagrangian Integrated Trajectorymodel(backward trajectory model)and surface wind data,the transmission characteristics of atmospheric CO2 in Taiyuan are studied in various seasons.The results show that,in Taiyuan,the CO2 mole fraction in autumn and winter is higher than that in spring and summer,and on haze days is higher than that on non-haze days.The diurnal variation characteristic of CO2mole fraction in each season is‘single peak and single valley’with the peak value around 0700(hereafter refers to Beijing Time)and the valley value around 1600.The CO2 mole fraction on workdays is slightly higher than that on non-workdays and obviously different around 0800 of the early peak.Horizontal diffusion can reduce the CO2 mole fraction,while breezy weather is not beneficial to CO2 diffusion.The wind direction and speed in the upper levels are different from those near the surface,and the close air masses in the southwest–west–northwest sector raise the CO2 concentration in Taiyuan obviously.This indicates that the CO2 in Taiyuan is mainly contributed by local sources.

Silicon limitation on primary production and its destiny in Jiaozhou Bay, China Ⅷ: The variation of atmospheric carbon caused by both phytoplankton and human

Statistical analysis on data collected in the Jiaozhou Bay (Shandong, China) from May 1991 to February 1994 and those collected in Hawaii from March 1958 to December 2007 shows dynamic and cyclic changes in atmospheric carbon in the Northern Pacific Ocean (NPO), as well as the variation in space-time distribution of phytoplankton primary production and atmospheric carbon in the study regions. The study indicates that the human beings have imposed an important impact on the changing trends of the atmospheric carbon. Primary production in the Jiaozhou Bay presents a good example in this regard. In this paper, dynamic models of the atmospheric carbon in the NPO, the cyclic variations in the atmospheric carbon, and primary production in the Jiaozhou Bay are studied with simulation curves presented. A set of equations were established that able to calculate the rate and acceleration of increasing carbon discharged anthropologically into the atmosphere and the conversion rate of phytoplankton to atmospheric carbon. Our calculation shows that the amount of atmospheric carbon absorbed by one unit of primary production in the Jiaozhou Bay is (3.21–9.74)×10-9/(mgC·m-2d-1), and the amount of primary production consumed by a unit of atmospheric carbon is 102.66–311.52 (mgC·m-2d-1/10-6). Therefore, we consider that the variation of atmospheric carbon is a dynamic process controlled by the increase of carbon compound and its cyclic variation, and those from anthropologic discharge, and phytoplankton growth.

Evaluating effects of atmospheric CO_2 on stability of global climate:a cell-to-cell mapping approach

Atmospheric carbon dioxide concentration [CO2],incoming solar radiation and sea ice coverage are among the most important factors that control the global climate.By applying the simple cell-to-cell mapping technique to a simplified atmosphere-ocean-sea ice feedback climate model,effects of these factors on the stability of the climatic system are studied.The current climatic system is found to be stable but highly nonlinear.The resiliency of stability increases with [CO2] to a summit when [CO2] reaches 290 μL/L which is comparable to the pre-industrial level,suggesting carbon dioxide is essential to the stability of the global climate.With [CO2] rising further,the global climate stability decreases,the mean ocean temperature goes up and the sea ice coverage shrinks in the polar region.When the incoming solar radiation is intensified,the ice coverage gradually diminishes,but the mean ocean temperature remains relatively constant.Overall,our analysis suggests that at the current levels of three external factors the stability of global climate is highly resilient.However,there exists a possibility of extreme states of climate,such as a snow-ball earth and an ice-free earth.

Atmospheric Carbon Dioxide Reconstruction and Ocean Acidification Deduced from Carbon Isotope Variations across the Triassic–Jurassic Boundary in the Qiangtang Area, Tibetan Plateau

Objective The end-Triassic mass extinction was one of the five most profound Phanerozoic extinction events.This event was accompanied by a series of significant environmental changes,of which the most notable is the emergence of warm climate and the world-wide disappearance of carbonate platform.

A Method of Using a Carbon Fiber Spiral-Contact Electrode to Achieve Atmospheric Pressure Glow Discharge in Air

During discharge, appropriately changing the development paths of electron avalanches and increasing the number of initial electrons can effectively inhibit the formation of filamentary discharge. Based on the aforementioned phenomenon, we propose a method of using microdischarge electrodes to produce a macroscopic discharge phenomenon. In the form of an asymmetric structure composed of a carbon fiber electrode, an electrode structure of carbon fiber spiral-contact type is designed to achieve an atmospheric pressure glow discharge in air, which is characterized by low discharge voltage, low energy consumption, good diffusion and less ozone generation.

Preparation of Diamond-like Carbon Film Assisted in the Plasma of Dielectric Barrier Discharge at Atmospheric Pressure

Dielectric barrier discharge at atmospheric presure has been applied to prepare hydrocarbon films on large- area glass and silicon substrates. When hydrogen and methane mixture(2:1) is used as discharge gas and the substrate is heated to 300 C, hard hydrogenated amorphous carbon film is deposited. From the IR deconvolution analysis of the C-H stretching absorption for the coating, the hydrocarbon group ration (CH3:CH2:CH) and C-C bond type ratio (sp3c/sp2c) are about 10%: 21%: 69% and 3:1~6:1,respectively. Their Knoop hardness is up to 10Gpa. No film isdeposited when the content of methane in the mixed gases is decreased to 5% at 300 C silicon substrate.

New perspectives on deep carbon cycling

The proto-atmosphere serves as a crucial starting point for the carbon cycle.Estimations based on atmospheric data from Mars and Venus suggest that Earth's proto-atmosphere contained>110 bar of CO_(2)and>2.6 bar of nitrogen.The protoatmosphere had over 1000 bar of water vapor during the magma ocean stage,assuming the proto-ocean had a volume of two oceans of water.During this stage both water and carbon dioxide were in a supercritical state at the magma-atmosphere interface.Intense serpentinization reactions occurred due to rock-water interaction,producing abundant hydrogen.Consequently,nitrogen is reduced to ammonia,and carbon dioxide to methane,forming carbonate simultaneously.The proto-atmosphere dominated by methane,ammonia,and hydrogen formed a significant amount of amino acids through lightning.This process is essential not only to the origin of life,but also to the early carbon-nitrogen cycle on Earth.By the Hadean eon,a large amount of CO_(2)was sequestered as carbonate and organic material.Subsequently,it mainly entered the deep mantle through mantle overturn or subduction.In the mantle transition zone,carbonate undergoes“Redox freezing”,where carbonate is reduced to diamond through oxidation of ferrous iron in the melt.In the lower mantle,Fe^(2+)undergoes disproportionation reactions,forming Fe^(3+)and metallic iron.Among these,Fe^(3+)mainly resides in bridgmanite,thereby increasing the oxygen fugacity of the lower mantle,while metallic iron falls to the Earth's core.The distribution of carbon in the mantle is crucial for deep carbon cycling.The density curves of diamond and mantle peridotite melt intersect at the bottom of the mantle transition zone(about 660 km).This density crossover leads to the accumulation of diamond during the magma ocean stage.When materials such as subducting slabs enter the lower mantle,compensatory upwelling of lower mantle material occurs.Bridgmanite enters the upper mantle,decomposes,releasing Fe^(3+)ions and oxidizes diamond to carbonate,which under thermal disturbance from kimberlite and igneous carbonatites,moves upward.This carbonate layer may have caused significant topographic fluctuations at the 660 km boundary.Currently,diamond in this layer may still not have been completely oxidized to carbonate or carbon dioxide,serving as a redox buffering layer.This is a key factor in constraining deep carbon cycling.Subduction zones are important pathways for facilitating the cycling.Processes in the Earth's deep carbon cycle significantly influence the carbon content of surface reservoirs.The fluctuations in atmospheric CO_(2)content since the Neogene are closely linked to the uplift of the Tibetan Plateau and the subduction of the western Pacific Plate.Around 60 million years ago,the closure of the Neo-Tethys Ocean led to subduction of the Indian passive margin.The massive sediments on the Indian margin carried down large amounts of carbonate and organic material into the mantle,and the resulting volcanism released large amounts of greenhouse gases such as CO_(2)and methane into the atmosphere.The subduction of the Neo-Tethys Ocean passive margin weakened at about 51 Ma,and subduction of the western Pacific began.The depth of the western Pacific Ocean generally exceeds the carbonate compensation depth,and the amount of carbonate carried by subducting oceanic crust is minimal.Consequently,the input of subducted carbonate decreased significantly,leading to a substantial reduction in CO_(2)emissions from volcanoes.Based on volcanic data from the past12,000 years,the average rate of volcanic eruptions in subduction zones is estimated to be about 3 cubic kilometers per year.The weathering rate of volcanic ash is much higher than that of continental crust materials such as granite.The calcium,magnesium,and other ions provided by weathering of global volcanic ash are equivalent to the flux of global rivers into the oceans.The increase in volcanic ash and the decrease in CO_(2)emissions from subduction zones have led to a decrease in atmospheric CO_(2)levels,which is a key factor in the sustained global cooling since 51 million years ago.

Dynamics of Soil Organic Carbon Under Uncertain Climate Change and Elevated Atmospheric CO_2

Climate change and elevated atmospheric CO2 should affect the dynamics of soil organic carbon （SOC）. SOC dynamics under uncertain patterns of climate warming and elevated atmospheric CO2 as well as with different soil erosion extents at Nelson Farm during 1998-100 were simulated using stochastic modelling. Results based on numerous simulations showed that SOC decreased with elevated atmospheric temperature but increased with atmospheric CO2 concentration. Therefore, there was a counteract effect on SOC dynamics between climate warming and elevated CO2. For different soil erosion extents, warming 1℃ and elevated atmospheric CO2 resulted in SOC increase at least 15%, while warming 5 ℃ and elevated CO2 resulted in SOC decrease more than 29%. SOC predictions with uncertainty assessment were conducted for different scenarios of soil erosion, climate change, and elevated CO2. Statistically, SOC decreased linearly with the probability. SOC also decreased with time and the degree of soil erosion. For example, in 2100 with a probability of 50%, SOC was 1 617, 1 167, and 892 g m^-2, respectively, for no, minimum, and maximum soil erosion. Under climate warming 5 ℃ and elevated CO2, the soil carbon pools became a carbon source to the atmosphere （P 〉 95%）. The results suggested that stochastic modelling could be a useful tool to predict future SOC dynamics under uncertain climate change and elevated CO2.

Seasonal and diurnal variations of atmospheric peroxyacetyl nitrate, peroxypropionyl nitrate, and carbon tetrachloride in Beijing

Atmospheric peroxyacetyl nitrate （PAN）, peroxypropionyl nitrate （PPN）, and carbon tetrachloride （CCl4） were measured from September 2010 to August 2011 in Beijing. PAN exhibited low values from mid-autumn to early spring （October to March） with monthly average concentrations ranging from 0.28 to 0.73 ppbV, and increased from early spring to summer （March to August）, ranging from 1.37-3.79 ppbV. The monthly variation of PPN was similar to PAN, with low values （below detection limit to 0.18 ppbV） from mid-autumn to early spring, and a monthly maximum in September （1.14 ppbV）. The monthly variation of CCl4 was tightly related to the variation of temperature, exhibiting a minimum in winter （69.3 pptV） and a maximum of 180.6 pptV in summer. Due to weak solar intensity and short duration, PAN and O3 showed no distinct diurnal patterns from morning to night during winter, whereas for other seasons, they both exhibited maximal values in the late afternoon （ca. 15：00 to 16：00 local time） and minimal values during early morning and midnight. Good linear correlations between PAN and PPN were found in autumn （R = 0.91）, spring （R = 0.94）, and summer （R = 0.81）, with slopes of 0.130, 0.222, and 0.133, respectively, suggesting that anthropogenic hydrocarbons dominated the photochemical formation of PANs in Beijing. Positive correlation between PAN and O3 in summer with the low slopes （AO3/APAN） ranging from 9.92 to 18.0 indicated serious air pollution in Beijing, and strong negative correlation in winter reflected strong O3 consumption by NO titration and less thermal decompositin of PAN.

Study of atmospheric CO2 and CH4 at Longfengshan WMO/GAW regional station： The variations, trends, influence of local sources/sinks, and transport

Atmospheric CO_2 and CH_4 have been continuously measured since 2009 at Longfengshan WMO/GAW station(LFS) in China. Variations of the mole fractions, influence of long-distance transport, effects of local sources/sinks and the characteristics of synoptic scale variations have been studied based on the records from 2009 to 2013. Both the CO_2 and CH_4 mole fractions display increasing trends in the last five years, with growth rates of 3.1±0.02 ppm yr.1 for CO_2 and 8±0.04 ppb yr.1(standard error, 1-σ)for CH_4. In summer, the regional CO_2 mole fractions are apparently lower than the Marine Boundary Layer reference, with the lowest value of.13.6±0.7 ppm in July, while the CH_4 values are higher than the MBL reference, with the maximum of 139±6 ppb.From 9 to 17(Local time, LT) in summer, the atmospheric CO_2 mole fractions at 10 m a.g.l. are always lower than at 80 m, with a mean difference of.1.1±0.2 ppm, indicating that the flask sampling approach deployed may underestimate the background mole fractions in summer. In winter, anthropogenic emissions dominate the regional CO_2 and CH_4 mole fractions. Cluster analysis of backward trajectories shows that atmospheric CO_2 and CH_4 at LFS are influenced by anthropogenic emissions from the southwest(Changchun and Jilin city) all year. The synoptic scale variations indicate that the northeastern China plain acts as an important source of atmospheric CO_2 and CH_4 in winter.

Greenhouse gas emissions from oilfield-produced water in Shengli Oilfield,Eastern China

Greenhouse gas（GHG） emissions from oil and gas systems are an important component of the GHG emission inventory. To assess the carbon emissions from oilfield-produced water under atmospheric conditions correctly, in situ detection and simulation experiments were developed to study the natural release of GHG into the atmosphere in the Shengli Oilfield,the second largest oilfield in China. The results showed that methane（CH4） and carbon dioxide（CO2） were the primary gases released naturally from the oilfield-produced water.The atmospheric temperature and release time played important roles in determining the CH4 and CO2emissions under atmospheric conditions. Higher temperatures enhanced the carbon emissions. The emissions of both CH4 and CO2from oilfield-produced water were highest at 27°C and lowest at 3°C. The bulk of CH4 and CO2was released from the oilfield-produced water during the first release period, 0–2 hr, for each temperature, with a maximum average emission rate of 0.415 g CH4/（m3·hr） and 3.934 g CO2/（m3·hr）, respectively. Then the carbon emissions at other time periods gradually decreased with the extension of time. The higher solubility of CO2 in water than CH4 results in a higher emission rate of CH4 than CO2over the same release duration. The simulation proved that oilfield-produced water is one of the potential emission sources that should be given great attention in oil and gas systems.

Cooperative effect from cation and anion of pyridine-containing anion-based ionic liquids for catalysing CO_2 transformation at ambient conditions

Pyridine-containing anion-based ionic liquids(PA-ILs) with two kinds of interaction sites to bind CO_2, e.g., [P4444][2-OP], were found to be highly efficient for catalysing the cycloaddition reactions of atmospheric CO_2 with epoxides at room temperature under metal-and halogen-free conditions, producing a series of cyclic carbonates in high yields. It was demonstrated that the cooperative interaction from two interaction sites in the anions of PA-ILs activated CO_2, while the cation activated the epoxides substrates via coordination to the central P+ unit, thus resulting in the high activity of the IL catalysts.