新疆分布的国家重点保护野生植物地理成分及分布特征

根据2021年公布的《国家重点保护野生植物名录》统计分析了新疆分布的国家重点保护野生植物物种组成,并对这些植物的分布区类型以及水平和垂直分布特征进行了分析。结果表明:新疆分布的国家重点保护野生植物共有56种2变种,隶属于20科26属。在科水平上,百合科(Liliaceae)种类最多,有23种1变种;在属水平上,郁金香属(Tulipa Linn.)和贝母属(Fritillaria Linn.)种类较多,分别有14种1变种和8种。从分布区类型看,新疆分布的国家重点保护野生植物在属水平有5个分布型和8个亚型,在种水平有6个分布型和14个亚型;温带成分在属和种水平上均占有绝对优势,分别占新疆分布的国家重点保护野生植物总属数和总种数的70.8%和94.8%;在种水平上,特有成分有14种2变种,其中8种2变种为新疆特有分布。从新疆分布的国家重点保护野生植物的水平分布特征看,天山地区、阿尔泰地区和准噶尔地区(准噶尔西部山地亚地区和准噶尔盆地亚地区)分布的种类较多;其中天山地区分布的种类最多(37种),占新疆国家重点保护野生植物总种数的63.8%,且多数种类为重要经济植物资源。新疆分布的国家重点保护野生植物的垂直分布特征明显,在山地森林、山地草甸和山地草原分布的种类较多,尤其集中分布在海拔1600~2800 m的山地森林和山地草甸中;贝母属植物主要分布在山地草原和山地草甸中,大部分郁金香属植物分布在草原和低山地带。研究结果显示:新疆分布的国家重点保护野生植物具有明显的温带特征,并具有一定的特有成分;这些植物主要分布在天山、阿尔泰山和准噶尔西部山地的山地森林、山地草甸和山地草原垂直带中以及准噶尔盆地边缘。

A new heterojunction in photocatalysis:S-scheme heterojunction

To harness abundant and clean solar energy along with relieving energy and environmental issues,photocatalysis holds great promise.Semiconductor-based photocatalysts are crucial to its successful application.However,the photocatalytic efficiency based on a unitary semiconductor material falls short of expectations,mainly because of the rapid recombination of photogenerated electrons and holes.This originates in the extremely strong Columbic force between them.Moreover,it is impossible for a single photocatalyst to achieve wide light absorption and ample redox ability concurrently.

Highly efficient visible-light photocatalytic H2 evolution over 2D–2D Cd S/Cu7S4 layered heterojunctions

Converting solar energy into clean and sustainable chemical fuels is a promising strategy for exploiting renewable energy.The application of photocatalytic water splitting technology in hydrogen production is important for sustainable energy development and environmental protection.In this study,for the first time,2D Cu7S4 co-catalysts were coupled on the surface of a CdS nanosheet photocatalyst by a one-step ultrasonic-assisted electrostatic self-assembly method at room temperature.The as-fabricated 2D^-2D CdS/Cu7S4 layered heterojunctions were demonstrated to be advanced composite photocatalysts that enhance the water splitting efficiency toward hydrogen production.The highest hydrogen evolution rate of the 2D^-2D CdS/2%Cu7S4 binary heterojunction photocatalyst was up to 27.8 mmol g^-1 h^-1 under visible light irradiation,with an apparent quantum efficiency of 14.7%at 420 nm,which was almost 10.69 times and 2.65 times higher than those of pure CdS nanosheets(2.6 mmol g^-1 h^-1)and CdS-2%CuS(10.5 mmol g^-1 h^-1),respectively.The establishment of the CdS/Cu7S4 binary-layered heterojunction could not only enhance the separation of photogenerated electron-hole(e--h+)pairs,improve the transfer of photo-excited electrons,and prolong the life-span of photo-generated electrons,but also enhance the light absorption and hydrogen-evolution kinetics.All these factors are important for the enhancement of the photocatalytic activity.Expectedly,the 2D^-2D interface coupling strategy based on CdS NSs can be extensively exploited to improve the hydrogen-evolution activity over various kinds of conventional semiconductor NSs.

Constructing low-cost Ni3C/twin-crystal Zn0.5Cd0.5S heterojunction/homojunction nanohybrids for efficient photocatalytic H2 evolution

The development of low-cost semiconductor photocatalysts for highly efficient and durable photocatalytic H2 evolution under visible light is very challenging.In this study,we combine low-cost metallic Ni3C cocatalysts with twin nanocrystal Zn0.5Cd0.5S(ZCS)solid solution homojunctions for an efficient visible-light-driven H2 production by a simple approach.As-synthesized Zn0.5Cd0.5S-1%Ni3C(ZCS-1)heterojunction/homojunction nanohybrid exhibited the highest photocatalytic H2-evolution rate of 783μmol h‒1 under visible light,which is 2.88 times higher than that of pristine twin nanocrystal ZCS solid solution.The apparent quantum efficiencies of ZCS and ZCS-1 are measured to be 6.13%and 19.25%at 420 nm,respectively.Specifically,the homojunctions between the zinc blende and wurtzite segments in twin nanocrystal ZCS solid solution can significantly improve the light absorption and separation of photogenerated electron-hole pairs.Furthermore,the heterojunction between ZCS and metallic Ni3C NP cocatalysts can efficiently trap excited electrons from ZCS solid solution and enhance the H2-evolution kinetics at the surface for improving catalytic activity.This study demonstrates a unique one-step strategy for constructing heterojunction/homojunction hybrid nanostructures for a more efficient photocatalytic H2 evolution compared to other noble metal photocatalytic systems.

Ni-based photocatalytic H_2-production cocatalysts

Photocatalysis is believed to be one of the best methods to realize sustainable H2 production. However, achieving this through heterogeneous photocatalysis still remains a great challenge owing to the absence of active sites, sluggish surface reaction kinetics, insufficient charge separation, and a high thermodynamic barrier. Therefore, cocatalysts are necessary and of great significance in boosting photocatalytic H2 generation. This review will focus on the promising and appealing low-cost Ni-based H2-generation cocatalysts as the alternatives for the high-cost and low-abundance noble metal cocatalysts. Special emphasis has been placed on the design principle, modification strategies for further enhancing the activity and stability of Ni-based cocatalysts, and identification of the exact active sites and surface reaction mechanisms. Particularly, four types of modification strategies based on increased light harvesting, enhanced charge separation, strengthened interface interaction, and improved electrocatalytic activity have been thoroughly discussed and compared in detail. This review may open a new avenue for designing highly active and durable Ni-based cocatalysts for photocatalytic H2 generation.

Improved visible-light photocatalytic H_2 generation over CdS nanosheets decorated by NiS_2 and metallic carbon black as dual earth-abundant cocatalysts

CdS nanosheets(NSs)photocatalysts modified with dual earth‐abundant co‐catalysts of metallic carbon black(CB)and NiS2were synthesized by a two‐step solvothermal/impregnation method.Allthe experiment results demonstrated that the co‐loading of CB and NiS2could significantly enhance the photocatalytic H2‐evolution activity of CdS NSs.The photocatalytic performance of the as‐prepared CdS/CB/NiS2samples was tested under visible light(λ≥420nm)by using an aqueous solution containing0.25mol L–1Na2S‐Na2SO3as the sacrifice agent.The CdS‐0.5%CB‐1.0%NiS2composite photocatalysts exhibited the highest H2‐evolution rate of166.7μmol h?1,which was approximately5.16and1.87times higher than those of pure CdS NSs and CdS‐1.0%NiS2,respectively.The possible mechanism for the enhanced H2‐evolution activity of CdS/CB/NiS2composite photocatalysts was proposed.The results showed that the enhanced photocatalytic H2‐evolution activities could be ascribed to the co‐loading of metallic CB and NiS2as co‐catalysts onto the surface of CdS NSs.The excellent synergetic effect between the CB and NiS2could obviously improve visible light absorption,promote separation of photogenerated electron‐hole pairs and boost the H2‐evolution kinetics,thus leading to an enhanced activity for H2evolution.More interestingly,the metallic CB could not only act as a cocatalyst for H2evolution,but also serve as a conductive electron bridge to promote the charge migration.This work not only demonstrates that loading CB as a co‐catalyst is a promising strategy to further boost the photocatalytic activity of CdS/NiS2composites,but also offers a new mechanistic insight into the construction of highly efficient and stable CdS NSs‐based hybrid photocatalysts with dual earth‐abundant co‐catalysts for photocatalytic applications.

Composition and Regeneration of Trees in the Community Forests of Lamjung District,Nepal

The community forest program in Nepal is one of the successful conservation initiatives.Tree species in a forest ecosystem have a fundamental role in maintaining the vegetation structure,complexity,and heterogeneity.This study analyzes the composition and regeneration of tree species in five community forests(CFs)of the sub-tropical region,Lamjung district,Nepal for preparing baseline data for long-term research projects and helps the community to manage their CFs scientifically.Tree species data were generated by stratified random sampling using 35 quadrate plots(size:20 m x 20 m).The density of adult trees in the forests ranged from 575 Ind ha^(-1)(Tilahar CF)to 1196 Ind/ha(Deurali Thadopakha CF).The sapling ranged from 2533 Ind ha^(-1)(Tilahar CF)to 4000 Ind ha^(-1)(Thuliban CF)and seedling from 19583 Ind ha^(-1)(Tilahar CF)to 37500 Ind ha^(-1)(Thuliban CF).Similarly,the adult tree basal area varied from 28.34 m^(2) ha^(-1)(Tilahar CF)to 49 m^(2) ha^(-1)(Deurali CF).The adult tree diversity index(Shannon-Weiner’s H)also ranged from 1.08(Thuliban CF)to 1.88(Tilahar CF).The tree species such as Sapium insigne,Ficus benghalensis,Lagerstroemia parviflore,Albizia sp.and Pinus roxburghii were weak regeneration.In general,the forests have good regeneration status except for Tilahar Community Forest,but based on the DBH size class distribution diagram,there is no sustainable regeneration.Among the five community forests the DBH size of adults was significantly different,and the DBH of Deurali Thadopakha was the lowest.But only few species have good regeneration and most of the species have weak,poor to no regeneration.The dominancy of fewer species like Shorea robusta,Castanopsis indica,and Schima wallichii accordingly maintain the overall regeneration of tree of CFs,so further plantation needs to be done inside the CF by triage accordingly those species whose regeneration has poor.