Single‐atom‐alloys (SAAs), as an emerging kind of materials, combine the advantages of alloy and single‐atom catalysts. The full atomic utilization of active sites and well‐defined bonding ...environments in SAAs lead to superior electrocatalytic performance and give a deep insight into the structural–activity relationship. In this review, the recent advances of SAAs in various electrochemical reactions are highlighted for further designing of highly effective electrocatalysts. This review starts with an introduction to the fundamental concepts of several effects, which influence the electrocatalytic activities. Then the preparation and characterization methods on SAAs are listed and compared. Next, the recent advances of SAAs in hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, alcohol/hydrogen/formic acid oxidation reaction, carbon dioxide reduction reaction, etc. are illustrated and discussed in detail. Finally, the challenges and suggestions for the future development of SAAs in energy‐conversion electrocatalysis are presented.
Single‐atom‐alloys (SAAs) with atomically dispersed dopant sites on an inactive host are developed to facilitate a deep insight into the reaction mechanism and achieve the full exposure of active sites. In addition, the free‐atom‐like electronic structures of dopants in SAAs are far different from that of conventional bimetallic alloys, which may lead to an unprecedented catalytic performance.
Structurally ordered intermetallic phases have exhibited higher and higher electrocatalytic activity and stability than disordered alloys in many reactions such as the oxygen reduction reaction (ORR) ...and small-molecule (hydrogen, formic acid, or ethanol) oxidation reactions. The enhanced electrocatalytic activity could be derived from the definite composition and predictable control over structural, geometric, and electronic effects. This review, based on the understanding of the catalytic mechanism of structurally ordered intermetallic nanoparticles, provides a comprehensive acknowledgment of how the particle size and morphology affect the catalytic performance. The strategy for reducing particle size and the impact of particle size on electrocatalysis will be first introduced. Then, recent developments in the synthesis and design of morphology-controlled catalysts are summarized. The structure–activity relationship between the catalytic activity and morphology including core–shell/hollow and porosity will be highlighted. Finally, the current challenges and future developments are provided. On the basis of this review, intermetallic nanoparticles will shed light on the future development of electrocatalysts for fuel cells and metal-air batteries.
Increasing plant diversity can increase ecosystem functioning, stability, and services in both natural and managed grasslands, but the effects of herbivore diversity, and especially of livestock ...diversity, remain underexplored. Given that managed grazing is the most extensive land use worldwide, and that land managers can readily change livestock diversity, we experimentally tested how livestock diversification (sheep, cattle, or both) influenced multidiversity (the diversity of plants, insects, soil microbes, and nematodes) and ecosystem multifunctionality (including plant biomass production, plant leaf N and P, above-ground insect abundance, nutrient cycling, soil C stocks, water regulation, and plant–microbe symbiosis) in the world’s largest remaining grassland. We also considered the potential dependence of ecosystem multifunctionality on multidiversity. We found that livestock diversification substantially increased ecosystem multifunctionality by increasing multidiversity. The link between multidiversity and ecosystem multifunctionality was always stronger than the link between single diversity components and functions. Our work provides insights into the importance of multitrophic diversity to maintain multifunctionality in managed ecosystems and suggests that diversifying livestock could promote both multidiversity and ecosystem multifunctionality in an increasingly managed world.
A lithium–oxygen battery would deliver the highest energy density of a rechargeable battery, but the multiphase electrochemical reaction on the air cathode has difficulty proceeding when operated ...with only solid catalysts. We report here the organic-electrolyte-dissolved iron phthalocyanine (FePc) as a shuttle of (O2)− species and electrons between the surface of the electronic conductor and the insulator Li2O2 product of discharge. The Li2O2 is observed to grow and decompose without direct contact with carbon, which greatly enhances the electrochemical performance. Our results signal that the use of molecular shuttles that are catalytically active may prove to be enablers of a practical lithium–air rechargeable battery.
•Soil salinity was the best predictors of soil bacterial and fungal community structure.•Fungi are more sensitive to grassland degradation than bacteria.•Grassland degradation increases interactions ...among microorganisms.
Grassland degradation is a retrogressive successionofgrasslandvegetation, which leads to the loss of biodiversity and the degradation of ecosystem functions. Soil microbiomes play critical roles in the functioning and services of grassland ecosystems, yet little is known about how their diversity, structure and co-occurrence network characteristics respond to grassland degradation. Here, we used lllumina Miseq technique to evaluate soil bacterial and fungal communities in a meadow steppe with different degrees of degradation in Northeastern China. Our results showed that Actinobacteria, Proteobacteria, and Chloroflexi and Acidobacteria were the dominant bacterial phyla, while Ascomycota, Basidiomycota, and Zygomycota were the predominant fungal phyla. The relative abundance of taxa assigned to Actinobacteria, Gemmatimonadetes, Firmicutes, and Deinococcus-Thermus increased with increasing degradation degrees, whereas those affiliated with Acidobacteria and Nitrospirae showed a decreasing pattern. Compared to bacteria, the relative abundance of most fungal phyla decreased gradually along the degradation gradient. Bacterial Shannon diversity index possessed a similar hump pattern, while fungal diversity decreased with increasing degree of grassland degradation. Bacterial and fungal communities have different responses to grassland degradation, indicating that fungi are more sensitive to grassland degradation than bacteria. Both bacterial and fungal community structures were significantly different among the three sites. Changes in soil bacterial and fungal community structures were best explained by soil salinity and pH. Plant diversity and nitrogen concentration in aboveground plant tissues were also important factors for regulating fungal communities. Co-occurrence network analysis revealed that microbial taxa increased positive interactions and average degree to strengthen the adaptability of microorganisms to grassland degradation. These findings could enhance our understanding of the formation and maintenance of microbial community diversity in degraded grasslands and the development of a new indicator for grassland ecosystem management.
We have developed a template-free procedure to synthesize Co3O4 hollow-structured nanoparticles on a Vulcan XC-72 carbon support. The material was synthesized via an impregnation–reduction method ...followed by air oxidation. In contrast to spherical particles, the hollow-structured Co3O4 nanoparticles exhibited excellent lithium storage capacity, rate capability, and cycling stability when used as the anode material in lithium-ion batteries. Electrochemical testing showed that the hollow-structured Co3O4 particles delivered a stable reversible capacity of about 880 mAh/g (near the theoretical capacity of 890 mAh/g) at a current density of 50 mA/g after 50 cycles. The superior electrochemical performance is attributed to its unique hollow structure, which combines nano- and microscale properties that facilitate electron transfer and enhance structural robustness.
Novel N, S co-doped graphene (NSG) was prepared by annealing graphene oxide with thiourea as the single N and S precursor. The NSG electrodes, as efficient metal-free electrocatalysts, show a direct ...four-electron reaction pathway, high onset potential, high current density and high stability for the oxygen reduction reaction.
Background and aims
Understanding the influences of environmental variation and anthropogenic disturbance on soil respiration (
R
S
) is critical for accurate prediction of ecosystem C uptake and ...release. However, surprisingly, little is known about how soil respiration and its components respond to grazing in the context of global climate change (i.e., precipitation or nitrogen deposition increase).
Methods
We conducted a field manipulative grazing experiment with water and nitrogen addition treatments in a meadow grassland on the Songnen Plain, China, and assessed the combined influences of grazing and global change factors on
R
S
, autotrophic respiration (
R
A
), and heterotrophic respiration (
R
H
).
Results
Compared with the control plots,
R
S
,
R
A
and
R
H
all exhibited positive responses to water or nitrogen addition in the wet year, while a similar effect occurred only for
R
H
in the dry year. The responses of
R
S
to precipitation regimes were dominated by both frequency and amount. However, grazing significantly inhibited both soil respiration and its components in all subplots. Further analysis demonstrated that the plant root/shoot ratio, belowground biomass and microbial biomass played dominant roles in shaping these C exchange processes.
Conclusion
These findings suggest that changes in precipitation regimes, nitrogen deposition, and land utilization may significantly alter soil respiration and its component processes by affecting local carbon users (roots and soil microorganism) and carbon substrate supply in meadow steppe grasslands. The future soil carbon sequestration in the studied meadow steppe will be benefited more by the moderate grazing disturbance.
Clonal plants play key roles in maintaining community productivity and stability in many ecosystems. Connected individuals (ramets) of clonal plants can translocate and share, for example, ...photosynthates, water and nutrients, and such physiological integration may affect performance of clonal plants both in heterogeneous and homogeneous environments. However, we still lack a general understanding of whether or how physiological integration in clonal plants differs across homogeneous versus heterogeneous environments.
We compiled data from 198 peer‐reviewed scientific studies conducted in 19 countries with 108 clonal plant species from 35 families, and carried out a meta‐analysis of effects of physiological integration on 16 traits related to plant growth, morphology, physiology or allocation. Our analyses evaluated these relationships in (A) heterogeneous environments where at least one resource essential for plant growth (e.g. light, soil water and mineral nutrients) or non‐resource factor (e.g. grazing, trampling and burial) is spatially non‐uniformly distributed and (B) homogeneous environments where all these factors are spatially uniformly distributed.
Physiological integration increased growth of whole clones in both homogeneous and heterogeneous environments due to its highly significant contribution to growth of recipient ramets. Integration did not affect growth of donor ramets in heterogeneous environments, but decreased it in homogeneous environments.
Integration affected physiological traits of donor ramets in neither homogeneous nor heterogeneous environments. It did not affect any physiological traits of recipient ramets in homogeneous environments, but increased most of them in heterogeneous environments. For donor ramets, integration increased height by 53% and internode length by 37% in heterogeneous environments, but had no effect in homogeneous environments. For recipient ramets, integration increased height by 73% in homogeneous environments and by 115% in heterogeneous environments, and increased internode length by 35% only under heterogeneous environments. In heterogeneous environments, integration increased biomass allocation to roots of donor ramets under high water/nutrient conditions and decreased it under high light.
Physiological integration plays a strong role in clonal plant physiology, morphology and growth, especially for recipient ramets in heterogeneous environments. Therefore, physiological integration may have contributed to the widespread of clonal plants in nature and their dominance in many ecosystems. It may also play important roles in invasion success of alien clonal plants and in maintaining functions and stability of ecosystems where clonal plants are abundant.
A free Plain Language Summary can be found within the Supporting Information of this article.
A free Plain Language Summary can be found within the Supporting Information of this article.
1. It is well documented that large herbivores have pronounced effects on plant communities in grassland ecosystems, and the extent and course of their effects can largely depend on both plant and ...herbivore characteristics. Previous studies highlighted the importance of plant productivity in predicting the impact of herbivores on grasslands. Yet, there has been little consideration of how different herbivores affect plant communities that, in turn, differ in plant diversity. 2. In a 2-year grazing experiment, we tested the effects of large herbivores (cattle or sheep, or both together) on plant communities under high and low plant diversity levels in eastern Eurasian steppe. 3. We found that, for high plant diversity grassland, mixed grazing by cattle and sheep significantly increases plant diversity, but we found no effect of grazing by cattle or sheep alone. Grazing by cattle or sheep alone or mixed grazing by cattle and sheep did not significantly affect plant biomass in the high diversity grassland. However, for low plant diversity grassland, grazing by cattle alone and mixed grazing by cattle and sheep significantly increased plant diversity, but significantly decreased plant biomass. There was no significant impact on both plant diversity and biomass from sheep grazing. 4. Synthesis and applications. We conclude that the effects of grazing in grassland strongly depend on herbivore assemblages and pre-grazing plant diversity. Herbivore grazing might contribute more to the maintenance of grassland structure and ecosystem functioning under high plant diversity compared with low plant diversity. Furthermore, our data suggest that multiple-species mixed grazing regimes in grassland systems with high plant diversity could represent the optimal protocol for grazing management. This study emphasizes the importance of maintaining both plant and herbivore diversity to optimize ecosystem functioning.
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