Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispe...Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispersed Au_1 catalyst is synthesized and applied in electrochemical synthesis of ammonia under ambient conditions. A high NH+4 Faradaic efficiency of 11.1 % achieved by our Au_1 catalyst surpasses most of reported catalysts under comparable conditions. Benefiting from efficient atom utilization, an NH+4 yield rate of 1,305 μg h-1 mg-1Au has been reached, which is roughly 22.5 times as high as that by sup- ported Au nanoparticles. We also demonstrate that by employing our Au_1 catalyst, NH+4 can be electro- chemically produced directly from N_2 and H_2 with an energy utilization rate of 4.02 mmol kJ-1. Our study provides a possibility of replacing the Haber-Bosch process with environmentally benign and energy-efficient electrochemical strategies.展开更多
The accurate measurement of the dynamics of photosynthesis in China’s subtropical evergreen forest ecosystems is an important contribution to carbon(C) sink estimates in global terrestrial ecosystems and their respon...The accurate measurement of the dynamics of photosynthesis in China’s subtropical evergreen forest ecosystems is an important contribution to carbon(C) sink estimates in global terrestrial ecosystems and their responses to climate change. Eddy covariance has historically been the only direct method to assess C flux of whole ecosystems with high temporal resolution, but it suffers from limited spatial resolution. During the last decade, continuous global monitoring of plant primary productivity from spectroradiometer sensors on flux towers and satellites has extended the temporal and spatial coverage of C flux observations. In this study, we evaluated the performance of two physiological remote sensing indices, fluorescence reflectance index(FRI) and photochemical reflectance index(PRI), to measure the seasonal variations of photosynthesis in a subtropical evergreen forest ecosystem using continuous canopy spectral and flux measurements in the Dinghushan Nature Reserve in southern China.The more commonly used NDVI has been shown to be saturated and mainly affected by illumination(R^2=0.88, p <0.001), but FRI and PRI could better track the seasonal dynamics of plant photosynthetic functioning by comparison and are less affected by illumination(R^2=0.13 and R^2=0.51, respectively) at the seasonal scale. FRI correlated better with daily gross primary production(GPP) in the morning hours than in the afternoon hours, in contrast to PRI which correlated better with light-use efficiency(LUE) in the afternoon hours. Both FRI and PRI could show greater correlations with GPP and LUE respectively in the senescence season than in the recovery-growth season. When incident PAR was taken into account, the relationship between GPP and FRI was improved and the correlation coefficient increased from 0.22 to 0.69(p < 0.001). The strength of the correlation increased significantly in the senescence season(R^2=0.79, p < 0.001). Our results demonstrate the application of FRI and PRI as physiological indices for the accurate measurement of the seasonal dynamics of plant community photosynthesis in a subtropical evergreen forest, and suggest these indices may be applied to carbon cycle models to improve the estimation of regional carbon budgets.展开更多
The carbon and water cycle,an important biophysical process of terrestrial ecosystems,is changed by anthropogenic revegetation in arid and semiarid areas.However,there is still a lack of understanding of the mechanism...The carbon and water cycle,an important biophysical process of terrestrial ecosystems,is changed by anthropogenic revegetation in arid and semiarid areas.However,there is still a lack of understanding of the mechanisms of carbon and water coupling in intrinsic ecosystems in the context of human activities.Based on the CO,and H,O flux measurements of the desert steppe with the planted shrub Caragana liouana,this study explored the carbon and water flux coupling of the ecosystem by analyzing the variations in gross primary productivity(GPP),evapotranspiration(ET)and water use efficiency(WUE)and discussing the driving mechanisms of biological factors.The seasonal variation in climate factors induced a periodic variation pattern of biophysical traits and carbon and water fluxes.The GPP and ET fluctuated in seasons,but the WUE was relatively stable in the growing season.The GP,ET and WUE were significantly driven by global radiation(R,),temperature(T,and T),water vapor pressure deficit,leaf area index and plant water stress index(PWSI).However,R,temperature and PWSI were the most important factors regulating WUE.R,and temperature directly affected WUE with a positive effect but indirectly inhibited WUE by rising PWSl.Plant water stress inhibited photosynthesis and transpiration of the planted shrub community in the desert steppe.When the plant water stress exceeded a threshold(PWSI>0.54),the WUE would decrease since the GPP responded more quickly to the plant water stress than ET.Our findings suggest that policies related to large-scale carbon sequestration initiatives under afforestation must first fully consider the status of water consumption and WUE.展开更多
基金supported by the National Key R&D Program of China (2017YFA0208300)the National Natural Science Foundation of China (21522107, 21671180, 21521091, 21390393, U1463202, and 21522305)
文摘Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispersed Au_1 catalyst is synthesized and applied in electrochemical synthesis of ammonia under ambient conditions. A high NH+4 Faradaic efficiency of 11.1 % achieved by our Au_1 catalyst surpasses most of reported catalysts under comparable conditions. Benefiting from efficient atom utilization, an NH+4 yield rate of 1,305 μg h-1 mg-1Au has been reached, which is roughly 22.5 times as high as that by sup- ported Au nanoparticles. We also demonstrate that by employing our Au_1 catalyst, NH+4 can be electro- chemically produced directly from N_2 and H_2 with an energy utilization rate of 4.02 mmol kJ-1. Our study provides a possibility of replacing the Haber-Bosch process with environmentally benign and energy-efficient electrochemical strategies.
基金National Key Research and Development Program of China(2017YFC0503803)National Natural Science Foundation of China(41571192)+1 种基金Natural Science Foundation of Hebei,China(D2016302002)Science and Technology Planning Project of Hebei,China(17390313D)
文摘The accurate measurement of the dynamics of photosynthesis in China’s subtropical evergreen forest ecosystems is an important contribution to carbon(C) sink estimates in global terrestrial ecosystems and their responses to climate change. Eddy covariance has historically been the only direct method to assess C flux of whole ecosystems with high temporal resolution, but it suffers from limited spatial resolution. During the last decade, continuous global monitoring of plant primary productivity from spectroradiometer sensors on flux towers and satellites has extended the temporal and spatial coverage of C flux observations. In this study, we evaluated the performance of two physiological remote sensing indices, fluorescence reflectance index(FRI) and photochemical reflectance index(PRI), to measure the seasonal variations of photosynthesis in a subtropical evergreen forest ecosystem using continuous canopy spectral and flux measurements in the Dinghushan Nature Reserve in southern China.The more commonly used NDVI has been shown to be saturated and mainly affected by illumination(R^2=0.88, p <0.001), but FRI and PRI could better track the seasonal dynamics of plant photosynthetic functioning by comparison and are less affected by illumination(R^2=0.13 and R^2=0.51, respectively) at the seasonal scale. FRI correlated better with daily gross primary production(GPP) in the morning hours than in the afternoon hours, in contrast to PRI which correlated better with light-use efficiency(LUE) in the afternoon hours. Both FRI and PRI could show greater correlations with GPP and LUE respectively in the senescence season than in the recovery-growth season. When incident PAR was taken into account, the relationship between GPP and FRI was improved and the correlation coefficient increased from 0.22 to 0.69(p < 0.001). The strength of the correlation increased significantly in the senescence season(R^2=0.79, p < 0.001). Our results demonstrate the application of FRI and PRI as physiological indices for the accurate measurement of the seasonal dynamics of plant community photosynthesis in a subtropical evergreen forest, and suggest these indices may be applied to carbon cycle models to improve the estimation of regional carbon budgets.
基金the National Natural Science Foundation of China(41967027)the Natural Science Foundation of Ningxia Province(2022AAC02011)+2 种基金the Excellent Talents Support Program of Ningxia Province(RQoo12)the Key Research and Development Program of Ningxia Province(2021BEG02010)the Special Plan for Local Sci-Tech Development Guided by the Central Government of China.
文摘The carbon and water cycle,an important biophysical process of terrestrial ecosystems,is changed by anthropogenic revegetation in arid and semiarid areas.However,there is still a lack of understanding of the mechanisms of carbon and water coupling in intrinsic ecosystems in the context of human activities.Based on the CO,and H,O flux measurements of the desert steppe with the planted shrub Caragana liouana,this study explored the carbon and water flux coupling of the ecosystem by analyzing the variations in gross primary productivity(GPP),evapotranspiration(ET)and water use efficiency(WUE)and discussing the driving mechanisms of biological factors.The seasonal variation in climate factors induced a periodic variation pattern of biophysical traits and carbon and water fluxes.The GPP and ET fluctuated in seasons,but the WUE was relatively stable in the growing season.The GP,ET and WUE were significantly driven by global radiation(R,),temperature(T,and T),water vapor pressure deficit,leaf area index and plant water stress index(PWSI).However,R,temperature and PWSI were the most important factors regulating WUE.R,and temperature directly affected WUE with a positive effect but indirectly inhibited WUE by rising PWSl.Plant water stress inhibited photosynthesis and transpiration of the planted shrub community in the desert steppe.When the plant water stress exceeded a threshold(PWSI>0.54),the WUE would decrease since the GPP responded more quickly to the plant water stress than ET.Our findings suggest that policies related to large-scale carbon sequestration initiatives under afforestation must first fully consider the status of water consumption and WUE.