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.
•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.
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.
The rational design of cathode host materials is significant in fulfilling high-efficiency sulfur electrochemistry as well as boosting the energy density of lithium–sulfur (Li–S) batteries. Herein, ...we develop a stringed “tube on cube” nanohybrid (CPZC) with a ternary hierarchical architecture, which contains a fibrous carbon skeleton, highly porous carbon cube filler, and abundant CNT tentacles as an advanced matrix for sulfur electrodes. The as-developed CPZC delivers excellent conductivity, abundant active interfaces, and strong confinement to polysulfide, and thus is capable of significantly expediting the sulfur redox kinetics and promoting battery durability. The fabricated sulfur electrode achieves a superb rate capability up to 10C, outstanding cyclability over 2000 cycles, and more importantly, excellent performance under high a sulfur loading and sparing electrolyte with a high energy density of 348.8 W h kg
−1
and 327.6 W h L
−1
at the system level, which reveals its potential in promoting the practical application of Li–S batteries.
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.
Exploring highly efficient and cost-effective electrocatalysts for the oxygen evolution reaction (OER) is becoming increasingly important in the field of sustainable energy systems. In this work, a ...three dimensional (3D) hierarchical porous nickel and iron based sulfide (Ni-Fe-S) with a sea urchin-like morphology is synthesized by a facile sulfurization of Prussian blue analogue (PBA) precursors with a hydrothermal reaction and post-calcination treatment. The mass ratio of PBA and sulfur sources, the hydrothermal temperature and time, and the presence of hydrazine hydrate are found to be important factors for the formation of the unique sea urchin-like materials with the porous carbon layer and mixed phases of Fe
5
Ni
4
S
8
and NiS, which are conducive to fast mass and charge transfer along various directions, endow the materials with mixed valences, improve the electronic conductivity and prevent the agglomeration of nanostructured sulfides. Benefiting from these fascinating advantages, the optimal Ni-Fe-S catalyst exhibits excellent catalytic activities with an overpotential as low as 200 mV to attain a current density of 10 mA cm
−2
and good stability toward the OER. This work not only offers a facile strategy to prepare efficient transition metal based sulfides with excellent electrocatalytic activity for the OER but also extends the synthesis and application of PBA-derived nanostructured materials.
Nickel-iron sulfides with a sea urchin-like architecture are controllably synthesized and exhibit enhanced OER activities.
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.
PDF
