Ni-rich cathode materials can deliver higher energy density with a lower cost compared with other conventional layered oxide materials. However, the cycling performance of Ni-rich materials needs ...further improvement, and the irreversible phase transformation related to the cell failure is not fully understood yet. Although an H1H2H3 structural change process is revealed, a more specific explanation about the difference of these hexagonal phases is needed for deeper comprehension and further targeted modification of Ni-rich materials. In this work, the different phase transformation mechanisms of LiNi0.6Co0.2Mn0.2O2 (NCM622) and LiNi0.8Co0.1Mn0.1O2 (NCM811) are investigated by C X-ray diffraction (XRD) measurement, and the relationship between structural change and capacity degradation is discussed, showing that H3 phase can be harmful for cycling. In addition, 6Li solid state nuclear magnetic resonance (ss-NMR) experiments are carried out for detecting the Li chemical environment at different state of charge, and the data can be associated with structural change obtained from in operando XRD results. From the analysis mentioned above, a new explanation of H1/H2/H3 is given, and a relationship between long range and local structural change has been put forward for the first time.
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•The phase changes of NCM materials are studied by in operando XRD.•NMR reveals Li environment at different states of charge and discharge.•A more specific explanation of H1/H2/H3 phase has been put forward.•The relationship between long range and local structure has been built up.
The alternating current (AC) density induced by submarine cables, which are parallel to submarine pipelines, has nonnegligible effects on the sacrificial anode system of submarine pipeline. The ...objective of this work is to clarify the AC corrosion of aluminum alloy sacrificial anode. The weight loss tests show that the corrosion rate of aluminum alloy increases with the increase in AC density, whereas the corrosion pits are obvious and dense. The calculated AC current efficiency for aluminum alloy is obviously higher than that for carbon steel under the same condition. The analyses of polarization characteristics and local environment reveal that the activity of aluminum alloy increases under the combined action of alloying elements and AC interference. Furthermore, the surface characteristics verify that Al and the alloying elements (Zn or In) in the solid solution with aluminum are oxidized during the anodic half cycles of AC density. And the alkaline environment created by the cathodic reaction in the cathodic half cycles is beneficial to the dissolution of aluminum alloy. In the condition of high AC density, the vigorous gas evolution is observed on coupon surface, resulting in the formation of larger corrosion pits due to the intrinsic effects of the adsorbed hydrogen and hydrogen bubbles. These results provide a guidance to understand the mechanism of AC corrosion for aluminum alloy exposed to artificial simulated seawater environment.
•Afforestation increased the PLFA content and the G+:G− ratio but reduced the F:B ratio.•Spatial variations in microbes were indirectly governed by tree distribution.•Major drivers on spatial ...variations in microbial community varied with land use type.•Bacteria was more sensitive to local environmental drivers than fungi in woodland.
Land use change directly influences soil microbial communities by altering vegetation cover. However, how soil microbial community structure responds spatially to plant distribution within a land use type following afforestation remains unclear. Here, we investigated the spatial variations in soil microbial biomass e.g., bacteria (B), fungi (F), gram-positive bacteria (G+), and gram-negative bacteria (G−) and community composition (the F:B ratio and G+:G- ratio) in woodland, shrubland and adjacent open areas (i.e., control) in the Danjiangkou Reservoir of central China, using geostatistical methods and phospholipid fatty acid (PLFA) analysis. We also explored the underlying mechanisms of whether or not and how environmental drivers, including biotic factors (e.g., tree distribution, present litter and root biomass) and abiotic factors e.g., soil organic carbon (SOC) and total nitrogen (TN), soil pH, and soil moisture, regulated the spatial variations in these microbial properties using partial Mantel tests. Afforestation increased the PLFA content and the G+:G- ratio but reduced the F:B ratio compared to that of the open area. Spatial analysis revealed that spatial variations in microbial communities were governed by local environmental drivers affected by tree distribution. Generally, SOC was a critical control on microbial biomass and community composition in all land use types, but the major drivers varied with land use type. Soil pH, SOC and TN affected almost all types of microbial PLFAs in shrubland, whereas litter biomass, SOC and TN were selectively correlated with specific groups of PLFAs (mainly from bacteria) in woodland. Soil pH affected the F:B ratio rather than the G+:G- ratio in both woodland and shrubland, while root biomass, SOC and TN were proved to be determinants of the F:B ratio and G+:G- ratio in shrubland. Other than SOC, the soil pH and N level were the primary controls on spatial variations in microbial biomass following afforestation. Overall, our results revealed that tree distribution-induced shifts in local environments controlled the spatial variations in soil microbial community structure within one land use type, highlighting that the role of spatial heterogeneity in microbial communities has important implications for land management.
Precisely tailoring the distance between adjacent metal sites to match adsorption configurations of key species for the targeted reaction pathway is a great challenge in heterogeneous catalysis. ...Here, we report a proof‐of‐concept study on the atomically sites‐tailored pathway in Pd‐catalyzed acetylene hydrogenation, i.e., increasing the distance of adjacent Pd atoms (dPd‐a‐Pd) for configuration matching in acetylene semi‐hydrogenation against coupling. dPd‐a‐Pd is identified as a structural descriptor for describing the competitiveness for reaction pathways, and the increased dPd‐a‐Pd prefers the semi‐hydrogenation pathway due to simultaneously promoted C2H4 desorption and the destabilized transition state of the C2H3* coupling. Spectroscopic, kinetics and electronic structure studies reveal that increasing dPd‐a‐Pd to 3.31 Å delivers superior selectivity and stability due to energy matching and appropriate hybridization of Pd 4d with In 2s and, especially, 2p orbitals.
The distance between adjacent Pd atoms is theoretically and experimentally demonstrated to be significant for defining the reaction pathways for selective hydrogenation processes exemplified by acetylene semi‐hydrogenation here. Increasing the distance favors the formation of ethylene while restraining those of byproducts due to the simultaneously promoted C2H4 desorption and destabilized transition state of C2H3* coupling.
•Crop-local CO2 enrichment system was developed by modifying a fuel-burning generator.•The new system supplies CO2 from perforated tubes set in the interrow space.•Crop-local CO2 enrichment ...effectively raised canopy CO2 concentration of strawberry.•Crop-local CO2 enrichment increased marketable yield.•Fuel use efficiency was improved by crop-local CO2 enrichment.
In protected strawberry (Fragaria × ananassa Duch.) cultivation, CO2 enrichment is essential to enhance both fruit quality and yield. Fuel burning generators are commonly used to supply CO2 to entire commercial greenhouse space. However, methods that are less fuel-based are desired for contemporary agricultural practices. A new crop-local CO2 enrichment system using a modified fuel-burning generator has been developed to increase yields and decrease the fuel required for CO2 enrichment in greenhouse strawberry production. This crop-local CO2 enrichment (CLC) method directly supplies CO2 from perforated tubes set in the interrow space of the plant canopy. The effects of this technique on fruit quality, fruit yield, and fuel use efficiency have been examined in comparison with conventional CO2 enrichment (CC) practices. The CLC method increased CO2 concentration inside the plant canopy by 100–200 μmol mol–1 when compared with CC under the ventilating conditions by a roof window. This resulted in significant increases of approximately 10–26% in the average fruit weight, 13% in the cumulative fruit number, and 22% in cumulative marketable yield when compared to CC. Furthermore, cumulative fuel consumption was approximately 27% lower with the CLC method when compared to CC. These results indicate that CLC improves fuel use efficiency when compared with CC as it increased yields and decreased fuel consumption.
This work focuses on the EXAFS investigation of the local environment of lead and iron sorbed onto volcanic ash materials previously studied using XANES technique. Different compounds found in the ...composition of volcanic ash were used as the models in the EXAFS fitting procedure of the experimental EXAFS spectra collected at the Fe K edge and Pb L3 edge in the Fe- and Pb-sorbed volcanic ash samples. The results showed two types of interactions involving in the adsorption process of both samples. The first is related to iron or lead absorber with oxygen atoms in the first coordination shell. The second interaction occurred between the absorbers (Fe or Pb) and the backscatters (Fe or Pb) in the second shell. The local environment of the iron-sorbed element may have a cubic geometry with different crystallographic sites related to oxygen and iron atoms. On the other hand, the lead-sorbed element may be in orthorhombic geometry with different sites related to oxygen atoms and lead atoms. The adsorption mechanisms involved in the process of iron and lead sorption are ion exchange with probable chemisorption for iron and microprecipitation for lead.
•EXAFS study revealed that two types of interaction around iron related to the oxygen and iron atoms respectively, at the first and second shells.•The interactions concerning lead are the oxygen and lead atoms with the lead absorber respectively, at the first second coordination shells.•The local environment of iron sorbed metal may be in cubic geometry with Fe coordinated to oxygen and Fe atoms at the first and second shells.•The local environment of lead sorbed metal may be in orthorhombic geometry with Pb coordinated to oxygen and Pb atoms at the first and second shells.•New insights are provided by the EXAFS fitting procedure for the investigation of the metal-sorbed local structure in such a mixture compound.
Flow electrolyzers based on gas-diffusion electrodes (GDEs) have been increasingly employed to advance toward industry-relevant electrochemical CO2 reduction reaction (CO2RR) performance, though ...fundamental understanding of the GDE system is still lacking. Here, we propose that regulating local CO2 concentration on copper (Cu) surfaces is an effective and general strategy to promote C−C coupling in CO2RR. Local CO2 concentration could influence the surface coverage of ∗CO2, ∗H, and ∗CO, which affects the reaction pathways toward multi-carbon (C2+) products. Guided by mass-transport modeling, we have identified three approaches to modulate the local CO2 concentration in GDE-based electrolyzers: (1) catalyst layer structure, (2) feed CO2 concentration, and (3) feed flow rate. Utilizing Cu2O nanoparticles as the model catalysts, modulation of local CO2 concentration enabled an optimized faradaic efficiency toward C2+ products of up to 75.5% at 300 mA cm−2 and C2+ partial current density of up to 342 mA cm−2 in 1.0 M KHCO3.
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•Three ways to modulate local CO2 concentration in GDE flow electrolyzer•Providing moderate local CO2 concentration enabled optimal C2+ product selectivity•75.5% faradaic efficiency for C2+ products at 300 mA cm−2 in KHCO3 electrolyte•C2+ product selectivity showed significant sensitivity toward CO2 mass transport
Electrochemical CO2 reduction powered by renewable energy is a potential approach to cut CO2 emission while creating value to the society. The electrosynthesis of multi-carbon (C2+) products, such as ethylene, ethanol, and 1-propanol, from CO2 is desired because of the high energy density and large global markets of these products. In order to achieve selective conversion of CO2 into C2+ products, past studies have been focused on the design of catalysts and the tuning of local environment (e.g., pH, cations, and molecular additives). Here, we report that local CO2 concentration has been an overlooked factor that affects the selectivity toward C2+ products. Utilizing our control catalysts and a gas-diffusion electrode flow cell operated at industrially relevant activity in near-neutral electrolyte, we show that a high local CO2 concentration leads to a suboptimal selectivity. Instead, providing a moderate local CO2 concentration is effective in promoting C–C coupling toward C2+ products.
Local environment plays an important role in steering the reaction pathways in electrochemical CO2 reduction reaction. Here, we present three approaches to modulate local CO2 concentration in gas-diffusion electrode flow electrolyzers. Employing monodisperse Cu2O nanoparticles as the model catalysts, we demonstrate that providing a moderate local CO2 concentration is effective in promoting C–C coupling. Ultimately, this study serves as a rational guide to tune CO2 mass transport in gas-diffusion electrode electrolyzers for the optimal production of valuable multi-carbon molecules.
Research Summary
Platform companies use design changes to govern their participants. The success of a design change depends on participants' responses, which are influenced by their local ...environments. Our study focuses on an important aspect of the local environment—rural versus urban. Using data from a leading e‐commerce platform, we find that relative to urban sellers, rural sellers were particularly poor at adjusting to a major design change, resulting in a persistent performance gap. We attribute these misaligned responses to rural sellers' lack of local access to rich information. This study shows that sellers' local heterogeneity generates equivocal responses and carries unintended consequences for platform governance. It also enriches our understanding of digital inequality and algorithmic design by highlighting the importance of the “offline interface.”
Managerial Summary
Digital platforms frequently change their design rules (e.g., ranking algorithms) to guide the behavior of participants. However, participants are inherently heterogeneous, and their abilities to understand and follow a design change also vary across populations. This study examines a major design change on a leading e‐commerce platform. We find that, compared to urban sellers, rural sellers developed responses that detracted from the platform's design goals and resulted in lower sales. This study highlights the need for digital platforms to understand how participants' offline environments affect their online behavior. This study also shapes the conversation on digital inequality: despite being connected online, entrepreneurs in traditionally disadvantaged regions may still suffer from a lack of accessible local information channels.
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•Local environment of oxygen vacancies at MnO2 were regulated by the concentration of Mo doping.•Moderate Mo doping could generate effective oxygen vacancies Mn-Ov-Mo.•0.3MoMnO2 with ...abundant Mn-Ov-Mo sites exhibited excellent catalytic activity, cycling stability, and toxicity resistance.•Mn-Ov-Mo sites facilitate the dynamic equilibrium of oxygen adsorption and desorption, promoting the activation of O2.
The microenvironment of oxygen vacancies plays an important role in metal oxide catalysts for VOCs catalytic oxidation. A simple strategy was provided to tailor the local environment of oxygen vacancies over MnO2 via Mo doping engineering to enhance its catalytic activity. The 0.3MoMnO2 with Mo/Mn quality ratio of 0.3 showed superior catalytic oxidation performance of benzene and anti-toxicity (H2O, SO2, and particulate matter). Its benzene oxidation rate at 190℃ was 1.95 × 10−4 mol/g/h, which was about three and two times higher than that of MnO2 and 0.9MoMnO2, respectively. The Mn-Ov-Mo sites were experimentally verified as the dominant active centers on 0.3MoMnO2. Through DFT calculation, Mo doping could enhance the oxygen adsorption on oxygen vacancies of MnO2. The remarkably well activity of Mn-Ov-Mo was rationally explained by the moderate oxygen adsorption energy to maintain a dynamic equilibrium of oxygen adsorption and desorption, which enhanced the oxygen activation, thereby promoting the benzene catalytic oxidation. However, excessive Mo doping induced the formation of Mo-Ov-Mo, and its side-on oxygen adsorption configuration was not conducive to oxygen transfer. This work broadens the understanding of the relationship between the local environment of oxygen vacancies and catalytic activities, which is beneficial for the rational design of efficient VOCs catalysts.
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•H2O2 electrosynthesis optimized in a dual membrane electrode assembly.•Moderate catalyst loading enhances mass transport and accessible active sites.•Hydrophobic treatment reduces ...surface area but improves electrode stability.•Operating in recycle reduces H2O2 degradation in the solid electrolyte chamber.
Hydrogen peroxide (H2O2) synthesis via the electrocatalytic reduction of oxygen is a sustainable alternative to the energy-intensive anthraquinone oxidation process. The use of gas diffusion electrodes in dual membrane electrode assembly (MEA) solid electrolyte (SE) electrolyzers has substantially improved H2O2 production, but the influence of mass transport and local reaction environment on H2O2 performance in these cell architectures is still unclear and unoptimized. Herein, we investigate the impacts of electrode components and reactor operating conditions on the H2O2 performance and cell potential required to reach current densities up to 400 mA cm−2. Results show an intermediate catalyst loading of 2 mg cm−2 improves H2O2 production through balancing O2 diffusion and active site exposure. Hydrophobic treatment via fluoropolymer improves electrode stability, but addition of >15 wt% fluoropolymer worsens performance, likely by limiting active site accessibility at the catalyst-membrane interface. Moreover, decreasing O2 concentration from typical pure streams to match the composition of air has a negligible effect at moderate current densities (∼50 mA cm−2), but significantly impacts overall performance at higher current densities (∼200 mA cm−2). This work also highlights benefits of operating the reactor with a recycled product stream rather than tuning the flow rate of water over the SE to extremely low values to obtain high H2O2 concentrations, as the latter likely contributes to exacerbated H2O2 degradation in the electrolyzer. This work provides insights into how macroscale system properties in flow cell electrolyzers impact the local reaction environment and mass transport, which in turn dictate overall catalytic performance.
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