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Exploiting high-efficiency catalysts toward hydrogen evolution reaction (HER) is a significant assignment nowadays. We find a quick and straightforward means to produce large-scale g-C 3 N 4 , which does not use template and easily obtains uniform nanostructures. And, we fabricate onestep preparation of a non-noble-metal catalyst, consisting of carbon material and transition metal only, by coupling graphitic carbon nitride (g-C 3 N 4 ) with Ni. The results show that Ni/C 3 N 4 composite catalyst possesses coral-like structure and its unique morphology is in favor of electrochemical activity for HER. Simultaneously, the Ni/C 3 N 4 composite catalyst presented prominent activity on HER with a high exchange current density of 1.91 × 10 −4 A cm −2 , a low Tafel slope of 128 mV dec −1 and small overpotentials of 356 and 222 mV to reach current densities of 100 and 10 mA cm −2 , which are superior to those of the state-of-the-art HER-active Ni-based compositions, as well as majority other metal-free catalysts, and even rivaled the electrocatalytic property of commercial Pt/C catalyst.

Owing to the scarcity of platinum resources and their visible flaw with poor durability and severe anode methanol crossover, Pt-based catalysts for catalyzing ORR have been experiencing some problems lately. Hence, nonprecious metal catalysts which are expected to replace platinum-based catalysts have become popular green sustainable development topics. We chose a facile pyrolysis method for the synthesis of this material, making the resulting coating material present a state of effectively encapsulating all cobalt nanoparticles into slim nitrogen-doped carbon nanotubes after process optimization, and the cobalt content even reached 20.9 wt %. In the catalytic aspect, the optimized Co@NSCNTs show a half wave potential equivalent to Pt/C in alkaline medium. Then, better durability (after 60,000 s chronoamperometry, the current retention still remains 95%) and commendable resistance to methanol crossover performed than the literature confirmed. All these characteristics superior to Pt/C should be ascribed to large amounts of entire encapsulated structures and synergism between encapsulated Co nanocrystal and graphitic N-doped carbon nanotubes. The presence of abundant metal particles allows more surface carbon and nitrogen atoms to be activated, in favor of the adsorption and dissociation of O2, and then improving oxygen reduction reaction (ORR) catalysis.

The spatiotemporal variability of the Normalized Difference Vegetation Index (NDVI) of three vegetation types (alpine steppe, alpine meadow, and alpine desert steppe) across the Tibetan Plateau was analyzed from 1982 to 2013. In addition, the annual mean temperature (MAT) and annual mean precipitation (MAP) trends were quantified to define the spatiotemporal climate patterns. Meanwhile, the relationships between climate factors and NDVI were analyzed in order to understand the impact of climate change on vegetation dynamics. The results indicate that the maximum of NDVI increased by 0.3 and 0.2 % per 10 years in the entire regions of alpine steppe and alpine meadow, respectively. However, no significant change in the NDVI of the alpine desert steppe has been observed since 1982. A negative relationship between NDVI and MAT was found in all these alpine grassland types, while MAP positively impacted the vegetation dynamics of all grasslands. Also, the effects of temperature and precipitation on different vegetation types differed, and the correlation coefficient for MAP and NDVI in alpine meadow is larger than that for other vegetation types. We also explored the percentages of precipitation and temperature influence on NDVI variation, using redundancy analysis at the observation point scale. The results show that precipitation is a primary limiting factor for alpine vegetation dynamic, rather than temperature. Most importantly, the results can serve as a tool for grassland ecosystem management.

The spatiotemporal variability of the seasonal dynamics of the climate and vegetation index was analyzed, and the relationship between the vegetation index and various climate factors were explored across the Tibetan Plateau. Severe variations in mean temperature, accumulated precipitation, and the normalized difference vegetation index (NDVI) were observed in the spring, summer, autumn, and winter. It found that the maximum NDVI of the study area increased at rates of 0.5 % per 10 years for spring (March-May), 0.4 % per 10 years for summer (June-August), 1.3 % per 10 years for autumn (September-November), and 0.3 % per 10 years for winter (December-February). Moreover, the change trends for temperature and precipitation increased as a whole. We demonstrated the correlation among NDVI and mean temperature and accumulated precipitation, in season, with the results differing for each season.

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Materials with a layered structure have attracted tremendous attention because of their unique properties. The ultrathin nanosheet structure can result in extremely rapid intercalation/de-intercalation of Na ions in the charge–discharge progress. Herein, we report a manganese oxide with pre-intercalated K and Na ions and having flower-like ultrathin layered structure, which was synthesized by a facile but efficient hydrothermal method under mild condition. The pre-intercalation of Na and K ions facilitates the access of electrolyte ions and shortens the ion diffusion pathways. The layered manganese oxide shows ultrahigh specific capacity when it is used as cathode material for sodium-ion batteries. It also exhibits excellent stability and reversibility. It was found that the amount of intercalated Na ions is approximately 71% of the total charge. The prominent electrochemical performance of the manganese oxide demonstrates the importance of design and synthesis of pre-intercalated ultrathin layered materials.