We discuss the concepts, research methods, and infrastructure of watershed science. A watershed is a basic unit and possesses all of the complexities of the land surface system, thereby making it the best unit for pra...We discuss the concepts, research methods, and infrastructure of watershed science. A watershed is a basic unit and possesses all of the complexities of the land surface system, thereby making it the best unit for practicing Earth system science. Watershed science is an Earth system science practiced on a watershed scale, and it has developed rapidly over the previous two decades. The goal of watershed science is to understand and predict the behavior of complex watershed systems and support the sustainable development of watersheds. However, watershed science confronts the difficulties of understanding complex systems, achieving scale transformation, and simulating the co-evolution of the human-nature system. These difficulties are fundamentally methodological challenges. Therefore, we discuss the research methods of watershed science, which include the self-organized complex system method, the upscaling method dominated by statistical mechanics, Darwinian approaches based on selection and evolutionary principles, hydro-economic and eco-economic methods that emphasize the human-nature system co-evolution, and meta-synthesis for addressing unstructured problems. These approaches together can create a bridge between holism and reductionism and work as a group of operational methods to combine hard and soft integrations and capture all aspects of both natural and human systems. These methods will contribute to the maturation of watershed science and to a methodology that can be used throughout land-surface systems science.展开更多
Oxygen vacancy（VO） plays a vital role in semiconductor photocatalysis. Rutile TiO2 nanomaterials with controllable contents of VO（0–2.18%） are fabricated via an insitu solid-state chemical reduction strategy, wit...Oxygen vacancy（VO） plays a vital role in semiconductor photocatalysis. Rutile TiO2 nanomaterials with controllable contents of VO（0–2.18%） are fabricated via an insitu solid-state chemical reduction strategy, with color from white to black. The bandgap of the resultant rutile TiO2 is reduced from 3.0 to 2.56 e V, indicating the enhanced visible light absorption. The resultant rutile TiO2 with optimal contents of VO（2.07%） exhibits a high solar-driven photocatalytic hydrogen production rate of 734 μmol h-1, which is about four times as high as that of the pristine one（185 μmol h-1）. The presence of VOelevates the apparent Fermi level of rutile TiO2 and promotes the efficient electronhole separation obviously, which favor the escape of photogenerated electrons and prolong the life-time（7.6×103 ns） of photogenerated charge carriers, confirmed by scanning Kelvin probe microscopy, surface photovoltage spectroscopy and transient-state fluorescence. VO-mediated efficient photogenerated electron-hole separation strategy may provide new insight for fabricating other high-performance semiconductor oxide photocatalysts.展开更多
Nanocomposites composed of one-dimensional（1D） CdS nanowires（NWs） and 1 T-MoS2 nanosheets have been fabricated through a two-step solvothermal process. 5 mol% of MoS2 loading results in the best optical properties...Nanocomposites composed of one-dimensional（1D） CdS nanowires（NWs） and 1 T-MoS2 nanosheets have been fabricated through a two-step solvothermal process. 5 mol% of MoS2 loading results in the best optical properties,photoelectrochemical（PEC） as well as photocatalytic activities for hydrogen evolution reaction（HER）. Compared with pure CdS NWs, the optimized nanocomposite shows 5.5 times enhancement in photocurrent and 86.3 times increase for HER in the presence of glucose and lactic acid as hole scavengers.The enhanced PEC and HER activities are attributed to the intimate contact between MoS2 and CdS that efficiently enhances charge carrier separation. In addition, ultrafast transient absorption（TA） measurements have been used to probe the charge carrier dynamics and gain deeper insight into the mechanism behind the enhanced PEC and photocatalytic performance.展开更多
基金supported by Prof.Chen Fahurepresented by this paper was funded by the Major Research Plan of the National Natural Science Foundation of China(Grant Nos.91225302,91425303)the Cross-disciplinary Collaborative Teams Program for Science,Technology,and Innovation of the Chinese Academy of Sciences
文摘We discuss the concepts, research methods, and infrastructure of watershed science. A watershed is a basic unit and possesses all of the complexities of the land surface system, thereby making it the best unit for practicing Earth system science. Watershed science is an Earth system science practiced on a watershed scale, and it has developed rapidly over the previous two decades. The goal of watershed science is to understand and predict the behavior of complex watershed systems and support the sustainable development of watersheds. However, watershed science confronts the difficulties of understanding complex systems, achieving scale transformation, and simulating the co-evolution of the human-nature system. These difficulties are fundamentally methodological challenges. Therefore, we discuss the research methods of watershed science, which include the self-organized complex system method, the upscaling method dominated by statistical mechanics, Darwinian approaches based on selection and evolutionary principles, hydro-economic and eco-economic methods that emphasize the human-nature system co-evolution, and meta-synthesis for addressing unstructured problems. These approaches together can create a bridge between holism and reductionism and work as a group of operational methods to combine hard and soft integrations and capture all aspects of both natural and human systems. These methods will contribute to the maturation of watershed science and to a methodology that can be used throughout land-surface systems science.
基金supported by the Key Program Projects of the National Natural Science Foundation of China (21631004)the National Natural Science Foundation of China (51672073)
文摘Oxygen vacancy（VO） plays a vital role in semiconductor photocatalysis. Rutile TiO2 nanomaterials with controllable contents of VO（0–2.18%） are fabricated via an insitu solid-state chemical reduction strategy, with color from white to black. The bandgap of the resultant rutile TiO2 is reduced from 3.0 to 2.56 e V, indicating the enhanced visible light absorption. The resultant rutile TiO2 with optimal contents of VO（2.07%） exhibits a high solar-driven photocatalytic hydrogen production rate of 734 μmol h-1, which is about four times as high as that of the pristine one（185 μmol h-1）. The presence of VOelevates the apparent Fermi level of rutile TiO2 and promotes the efficient electronhole separation obviously, which favor the escape of photogenerated electrons and prolong the life-time（7.6×103 ns） of photogenerated charge carriers, confirmed by scanning Kelvin probe microscopy, surface photovoltage spectroscopy and transient-state fluorescence. VO-mediated efficient photogenerated electron-hole separation strategy may provide new insight for fabricating other high-performance semiconductor oxide photocatalysts.
基金financially supported by the National Natural Science Foundation of China (51402126)support from Delta Dental Health Associates, NASA through MACES (NNX15AQ01A)UCSC Committee on Research Special Research Grant
文摘Nanocomposites composed of one-dimensional（1D） CdS nanowires（NWs） and 1 T-MoS2 nanosheets have been fabricated through a two-step solvothermal process. 5 mol% of MoS2 loading results in the best optical properties,photoelectrochemical（PEC） as well as photocatalytic activities for hydrogen evolution reaction（HER）. Compared with pure CdS NWs, the optimized nanocomposite shows 5.5 times enhancement in photocurrent and 86.3 times increase for HER in the presence of glucose and lactic acid as hole scavengers.The enhanced PEC and HER activities are attributed to the intimate contact between MoS2 and CdS that efficiently enhances charge carrier separation. In addition, ultrafast transient absorption（TA） measurements have been used to probe the charge carrier dynamics and gain deeper insight into the mechanism behind the enhanced PEC and photocatalytic performance.
