Search

Single-atom catalysts (SACs) for the hydrogen evolution reaction (HER) is an efficient electrochemical pathway to produce the green production. However, the development of HER process is hampered by the lack of high-performance electrocatalysts. In this work, we proposed a new π-d conjugated structure of the Ti3B3N3S6 monolayer as the single-atom catalysts for the HER process by using the density functional theory (DFT) calculations. The calculated results show that the Ti atom is active site of the Ti3B3N3S6 monolayer with the high catalytic activity (ΔGH = –0.14 eV) for HER. The electronic properties of the Ti3B3N3S6 monolayer were explored by the electron localization function (ELF), Bader charge analysis and the polarized density of states (PDOS) density analysis. The Ti3B3N3S6 monolayer can promote the electronic transfer during the HER process, which indicates taht the Ti3B3N3S6 monolayer can is considered to investigate the catalytic activity for HER. The Gibbs free energy of H atoms adsorption on the Ti3B3N3S6 monolayer is –0.14 eV. Furthermore, the origin of high catalytic activity for the Ti3B3N3S6 monolayer was explored by the analysis the PDOS of the H adsorption on the Ti3B3N3S6 monolayer. Therefore, our work propose a new and high catalytic single-atom catalyst for the HER.

Single–atom catalysts (SACs) have attracted wide attention to be acted as potential electrocatalysts for nitrogen reduction reaction (NRR). However, the coordination environment of the single transition metal (TM) atoms is essential to the catalytic activity for NRR. Herein, we proposed four types of 3‐, 4‐coordinated and π–d conjugated TMxB3N3S6 (x=2, 3, TM=Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Tc, Ru, Hf, Ta, W, Re and Os) monolayers for SACs. Based on density functional theory (DFT) calculations, I‐TM2B3N3S6 and III‐TM3B3N3S6 are the reasonable 3‐coordinated and 4‐coordinated structures screening by structure stable optimizations, respectively. Next, the structural configurations, electronic properties and catalytic performances of 30 kinds of the 3‐coordinated I‐TM2B3N3S6 and 4‐coordinated III‐TM3B3N3S6 monolayers with different single transition metal atoms were systematically investigated. The results reveal that B3N3S6 ligand is an ideal support for TM atoms due to existence of strong TM‐S bonds. The 3‐coordinated I‐V2B3N3S6 is the best SAC with the low limiting potential (UL) of −0.01 V, excellent stability (Ef=−0.32 eV, Udiss=0.02 V) and remarkable selectivity characteristics. This work not only provides novel π–d conjugated SACs, but also gives theoretical insights into their catalytic activities and offers reference for experimental synthesis. [ABSTRACT FROM AUTHOR]

The alpine grassland ecosystem is a critical part of the Qinghai‐Tibet Plateau (QTP), mainly including alpine meadows and alpine steppes. However, the influence factors of alpine grassland biodiversity are not clear for different alpine grassland types. In this study, pathway analysis was applied to explore the influences of soil, topography, climate, and human factors on alpine grassland biodiversity. Then, by using the geographically weighted regression (GWR) model, the spatial sensitivity response of alpine grassland biodiversity to soil, topography, climate, and human activities was revealed in different grassland types. The results were as follows: (1) The data and pathway analysis passed the validity and reliability analysis, indicating that the model fit of alpine grassland biodiversity was good for different grassland types. (2) For alpine meadows, the total effect coefficients of altitude, slope, and topographic wetness index (TWI) on normalized difference vegetation index (NDVI) (net primary productivity [NPP]) were 0.50, 0.21, and −0.48 (0.59, 0.17, and −0.41), respectively, suggesting that altitude had the strongest and positive effect on alpine meadow diversity. In addition, among human activity and climate variables, human activity intensity and precipitation exhibited significant effects on NDVI (NPP), with total effect coefficients of −0.17 and 0.61 (−0.19 and 0.63). The influence of soil, topography, climate, and human variables on alpine steppe diversity showed similarities with alpine meadow diversity. (3) Alpine grassland biodiversity was directly and indirectly influenced by multiple driving factors for different grassland types. The total coefficients of soil, topography, climate, and human factors on NDVI (NPP) were 0.41, 0.38, −0.21, and 0.71 (0.32, 0.50, −0.21, and 0.91), respectively, which indicated that alpine meadow diversity was mainly regulated by climate on the QTP, consistent with alpine steppe diversity. (4) For different grassland types, the spatial effects of various driving factors on alpine grassland biodiversity all showed significant spatial heterogeneity at the grid scale. Based on the knowledge about the driving mechanism and spatial response of alpine grassland biodiversity to its driving factors in different grassland types of the QTP, we aim to provide guidance for alpine grassland biodiversity conservation and rational ecosystem management. [ABSTRACT FROM AUTHOR]

As the 'third pole' of the world, the Qinghai‐Tibetan Plateau (QTP) is extremely ecologically sensitive and fragile, while also facing increasing levels of human activity, especially overgrazing. In this study, livestock data from the statistical yearbook were transformed to 1 km grazing intensity raster data by integrating the net primary productivity (NPP) data for 1990, 1995, 2000, 2005, 2010 and 2015. Furthermore, the human activity intensity (HAI) data at 1 km resolution were evaluated by the entropy weight method, which applied eight types of spatial data, including grazing intensity, Night‐Time Light, population density, Gross Domestic Product (GDP) density, the ratio of cultivated land, distance to road, distance to town and the slope of the Normalized Difference Vegetation Index (NDVI). Also, the five‐year interval human activity intensity data on the QTP from 1990 to 2015 were evaluated. By preparing the historical spatial data sets of grazing intensity and human activity intensity, our study will help to explore the influence of human disturbance on the alpine ecosystems on the QTP, as well as provide effective support for the decision‐making of the government aiming to achieve regional ecosystem management and sustainable development. [ABSTRACT FROM AUTHOR]