Metal‐free electrocatalysts have been extensively developed to replace noble metal Pt and RuO2 catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in fuel cells or ...metal–air batteries. These electrocatalysts are usually deposited on a 3D conductive support (e.g., carbon paper or carbon cloth (CC)) to facilitate mass and electron transport. For practical applications, it is desirable to create in situ catalysts on the carbon fiber support to simplify the fabrication process for catalytic electrodes. In this study, the first example of in situ exfoliated, edge‐rich, oxygen‐functionalized graphene on the surface of carbon fibers using Ar plasma treatment is successfully prepared. Compared to pristine CC, the plasma‐etched carbon cloth (P‐CC) has a higher specific surface area and an increased number of active sites for OER and ORR. P‐CC also displays good intrinsic electron conductivity and excellent mass transport. Theoretical studies show that P‐CC has a low overpotential that is comparable to Pt‐based catalysts, as a result of both defects and oxygen doping. This study provides a simple and effective approach for producing highly active in situ catalysts on a carbon support for OER and ORR.
Edge‐rich, oxygen‐functionalized graphene can be in situ generated on the surface of carbon fibers by Ar‐plasma etching. Both oxygen doping and defects contribute significantly to enhanced electrocatalytic activity for the oxygen reduction reaction and oxygen evolution reaction.
Co‐based spinel oxides, which are of mixing valences with the presence of both Co2+ and Co3+ at different atom locations, are considered as promising catalysts for the electrochemical oxidation of ...5‐hydroxymethylfurfural (HMF). Identifying the role of each atom site in the electroxidation of HMF is critical to design the advanced electrocatalysts. In this work, we found that Co2+Td in Co3O4 is capable of chemical adsorption for acidic organic molecules, and Co3+Oh play a decisive role in HMF oxidation. Thereafter, the Cu2+ was introduced in spinel oxides to enhance the exposure degree of Co3+ and to boost acidic adsorption and thus to enhance the electrocatalytic activity for HMF electrooxidation significantly.
The exploration of optimal geometrical site in Co3O4 for electrochemical HMF oxidation by the building tetrahedral (Zn2+) and octahedral (Al3+) blocks is described. The electrochemical results demonstrate that Co3+Oh are the best geometrical sites for HMF oxidation, and the chemical adsorption for acidic organic molecules is dominated by Co2+Td. The exposure degree of Co3+ is improved by Cu2+ and thus results in a record activity.
The exact role of a defect structure on transition metal compounds for electrocatalytic oxygen evolution reaction (OER), which is a very dynamic process, remains unclear. Studying the ...structure–activity relationship of defective electrocatalysts under operando conditions is crucial for understanding their intrinsic reaction mechanism and dynamic behavior of defect sites. Co3O4 with rich oxygen vacancy (VO) has been reported to efficiently catalyze OER. Herein, we constructed pure spinel Co3O4 and VO-rich Co3O4 as catalyst models to study the defect mechanism and investigate the dynamic behavior of defect sites during the electrocatalytic OER process by various operando characterizations. Operando electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) implied that the VO could facilitate the pre-oxidation of the low-valence Co (Co2+, part of which was induced by the VO to balance the charge) at a relatively lower applied potential. This observation confirmed that the VO could initialize the surface reconstruction of VO–Co3O4 prior to the occurrence of the OER process. The quasi-operando X-ray photoelectron spectroscopy (XPS) and operando X-ray absorption fine structure (XAFS) results further demonstrated the oxygen vacancies were filled with OH• first for VO–Co3O4 and facilitated pre-oxidation of low-valence Co and promoted reconstruction/deprotonation of intermediate Co–OOH•. This work provides insight into the defect mechanism in Co3O4 for OER in a dynamic way by observing the surface dynamic evolution process of defective electrocatalysts and identifying the real active sites during the electrocatalysis process. The current finding would motivate the community to focus more on the dynamic behavior of defect electrocatalysts.
Northeast China (NEC) accounts for about 30% of the nation's maize production in China. In the past three decades, maize yields in NEC have increased under changes in climate, cultivar selection and ...crop management. It is important to investigate the contribution of these changing factors to the historical yield increases to improve our understanding of how we can ensure increased yields in the future. In this study, we use phenology observations at six sites from 1981 to 2007 to detect trends in sowing dates and length of maize growing period, and then combine these observations with in situ temperature data to determine the trends of thermal time in the maize growing period, as a measure of changes in maize cultivars. The area in the vicinity of these six sites accounts for 30% of NEC's total maize production. The agricultural production systems simulator, APSIM‐Maize model, was used to separate the impacts of changes in climate, sowing dates and thermal time requirements on maize phenology and yields. In NEC, sowing dates trended earlier in four of six sites and maturity dates trended later by 4–21 days. Therefore, the period from sowing to maturity ranged from 2 to 38 days longer in 2007 than it was in 1981. Our results indicate that climate trends alone would have led to a negative impact on maize. However, results from the adaptation assessments indicate that earlier sowing dates increased yields by up to 4%, and adoption of longer season cultivars caused a substantial increase in yield ranging from 13% to 38% over the past 27 years. Therefore, earlier sowing dates and introduction of cultivars with higher thermal time requirements in NEC have overcome the negative effects of climate change and turned what would have otherwise been a loss into a significant increase in maize yield.
Northeast China (NEC) is not only one of the major agricultural production areas in China, but it is also the most susceptible to climate variability. This led us to investigate the impact of climate ...change on maize potential yield and yield gaps in this region, where maize accounts for about 30% of the nation's production. The APSIM‐Maize model was calibrated and validated for maize phenology and yields. The validated model was then used to estimate potential yields, rain‐fed potential yields, and yield gaps for assessing the climate impacts on maize productivity in NEC. During maize growing seasons from 1981 to 2010, the analysis indicates a warming trend all across NEC, whereas the trends in solar radiation and total precipitation tended to decrease. When the same hybrid was specified in APSIM for all years, a simulated increase of maximum temperature resulted in a negative impact on both potential yield and rain‐fed potential yield. A simulated increase in minimum temperature produced no significant changes in potential or rain‐fed potential yield. However, the increase of minimum temperature was shown to result in a positive impact on the on‐farm yield, consistent with our finding that farmers adopted longer season hybrids for which the increase in minimum temperature provided better conditions for germination, emergence, and grain filling during night time. The gap between potential and rain‐fed potential yields was shown to be larger at locations with lower seasonal precipitation (<500 mm). Our results indicate that regions with the largest yield gaps between rain‐fed potential and on‐farm yields were located in the southeast of NEC. Within NEC, on‐farm maize yields were, on average, only 51% of the potential yields, indicating a large exploitable yield gap, which provides an opportunity to significantly increase production by effective irrigation, fertilization, herbicide, and planting density in NEC.
Northeast China (NEC) is one of the major agricultural production areas in China and also an obvious region of climate warming. We were motivated to investigate the impacts of climate warming on the ...northern limits of maize planting. Additionally, we wanted to assess how spatial shifts in the cropping system impact the maize yields in NEC. To understand these impacts, we used the daily average air temperature data in 72 weather stations and regional experiment yield data from Jilin Province. Averaged across NEC, the annual air temperature increased by 0.38 °C per decade. The annual accumulated temperature above 10 °C (AAT10) followed a similar trend, increased 66 °C d per decade from 1961 to 2007, which caused a northward expansion of the northern limits of maize. The warming enabled early-maturing maize hybrids to be sown in the northern areas of Heilongjiang Province where it was not suitable for growing maize before the warming. In the southern areas of Heilongjiang Province and the eastern areas of Jilin Province, the early-maturing maize hybrids could be replaced by the middle-maturing hybrids with a longer growing season. The maize in the northern areas of Liaoning Province was expected to change from middle-maturing to late-maturing hybrids. Changing the hybrids led to increase the maize yield. When the early-maturing hybrids were replaced by middle-maturing hybrids in Jilin Province, the maize yields would increase by 9.8 %. Similarly, maize yields would increase by 7.1 % when the middle-maturing hybrids were replaced by late-maturing hybrids.
Cobalt oxides as efficient oxygen evolution reaction (OER) electrocatalysts have received much attention because of their rich reserves and cheap cost. There are two common cobalt oxides, Co3O4 ...(spinel phase, stable but poor intrinsic activity) and CoO (rocksalt phase, active but easily be oxidatized). Constructing Co3O4/CoO heterophase can inherit both characteristic features of each component and form a heterophase interface facilitating charge transfer, which is believed to be an effective strategy in designing excellent electrocatalysts. Herein, an atomic arrangement engineering strategy is applied to improve electrocatalytic activity of Co3O4 for the OER. With the presence of oxygen vacancies, cobalt atoms at tetrahedral sites in Co3O4 can more easily diffuse into interstitial octahedral sites to form CoO phase structure as revealed by periodic density functional theory computations. The Co3O4/CoO spinel/rocksalt heterophase can be in situ fabricated at the atomic scale in plane. The overpotential to reach 10 mA cm−2 of Co3O4/CoO is 1.532 V, which is 92 mV smaller than that of Co3O4. Theoretical calculations confirm that the excellent electrochemical activity is corresponding to a decline in average p‐state energy of adsorbed‐O on the Co3O4/CoO heterophase interface. The reaction Gibbs energy barrier has been significantly decreased with the construction of the heterophase interface.
A Co3O4/CoO heterophase interface at the atomic scale is elaborately constructed by incorporating oxygen vacancies. Theoretical calculation proves that with the existence of oxygen vacancies, the energy barrier for Co atom diffusion from tetrahedron sites to neighboring interstitial octahedron sites is dramatically decreased indicating more favorable formation of CoO. With the formation of the Co3O4/CoO heterophase interface, oxygen evolution reaction activity is enhanced effectively.
Against the background of global warming, extreme agrometeorological events have become more intense and frequent during the growing season of maize (
Zea mays
L.). In this study, we focused on the ...five types of extreme agrometeorological events that greatly affect maize production in Northeast China, including chilling injury, drought, rainstorm, frost, and gale. We averaged the actual timing of phenological events from the study agrometeorological stations and divided the maize growing season into four growth stages: emergence—jointing, jointing—flowering, flowering—kernel milk, and kernel milk—physiological maturity. Based on the historical weather data from 1960 to 2017 in the study region, we derived the values of pertinent indices for the five types of study extreme agrometeorological events during the four selected maize growth stages. The results showed that chilling injury and drought were relatively more frequent during the four growth stages of maize from 1960 to 2017 in the Northeast China. As time goes on during the growing season of maize, the spatial coverage of chilling injury, frost, and gale all showed a decreasing trend. By contrast, the spatial coverage of drought showed an increasing trend during the study growth stages of maize. During growth stages of maize, chilling injury was the main extreme agrometeorological event before the 2000s, while drought became the main extreme agrometeorological event after the 2000s. Identifying the main extreme climate events that could cause yield loss is imperative, and it is important for farmers to acknowledge ongoing changes in these extreme climate events in order to take preventive measures if necessary.
•Yield gap decreased to 3tha−1 in 2001–2010 with a rate of −69kgha−1 per year.•The spatiotemporal pattern of on-farm yield and potential yield was studied.•On-farm yield has substantially contributed ...to YG spatiotemporal variation.•The region for higher yield increase potential was given.
The yield gap (YG) between the potential yields (Yp) and the average on-farm yields (Ya) is an indicator of the potential improvement for crop production. Understanding how large the current gap is and how this gap has changed over the past few decades is essential for increasing wheat production to meet increased food demand in China. This paper describes a study conducted using an APSIM-Wheat model and farm-level crop yield to analyze the spatio-temporal distribution of the yield gap of winter wheat from 1981 to 2010 in the North China Plain. Nine varieties were calibrated and evaluated based on the data from 16 agro-meteorological experimental sites and then potential yields were estimated considering cultivar replacement. In addition, a trend pattern analysis of on-farm yields for the period 1981–2010 was conducted. Results revealed an estimated yield gap across the entire North China Plain region of 1140–6810kgha−1, with a weight average of 3630kgha−1 in 1981–2010. Expressed as a relative yield (yield gap % of potential yields), the range was 15–80%, and the weight average was 45%. Despite the negative effects of increasing temperature and decreasing radiation, the potential yields significantly increased by 45kgha−1 per year due to cultivar improvement. On-farm yields increased even more notably because of new cultivar selection, increased fertilizer application and other management improvements, but were stagnating in 32.3% of wheat areas, located mainly in Hebei province, Shandong province, Beijing and Tianjin. The improvement of on-farm yields have substantially contributed to yield gap spatio-temporal variation. As a result, the yield gap decreased from 4200kgha−1 (56%) in 1981–1990 to 3000kgha−1 (35%) in 2001–2010 at a rate of −69kgha−1 per year. However, yields stagnation will expand to the northern Henan province without cultivar potential productivity improving, where yield gap was close to or less than 20% of the potential yields and proved difficult to reduce. To further improve the total production of winter wheat in the coming decades, efforts should be paid to break the potential ceiling and reduce the yield gap by breeding higher yield variety and introduction of new agricultural technology.
Myasthenia gravis (MG) is an autoimmune disease caused by autoantibodies that is dependent on T-cell immunity and complement participation and mainly involves neuromuscular junctions. In this study, ...30 patients with myasthenia gravis were selected and divided into pretreatment (Case group) and posttreatment (Treatment group) and 30 healthy volunteers (CON group) were included. Among them, the treatment group was treated with Modified Buzhong Yiqi Decoction (MBZYQD), and the levels of antibodies such as AChR, Musk and Titin in blood and intestinal microbiota were compared before treatment (Case group), after treatment (Treatment group) and in healthy volunteers (CON group). The results showed that after treatment with MBZYQD, the antibody levels of AChR, MuSK, and Titin and the inflammatory factor level of IL-6, IL-1β, and IL-22 in MG patients decreased significantly and nearly returned to a healthy level. In addition, after treatment with MBZYQD, the diversity, structure and function of intestinal microorganisms in MG patients also recovered to a healthy level. At the phylum level, the relative abundance of Proteobacteria in the Case group increased significantly, accompanied by a significant decrease in the relative abundance of Bacteroides compared with that in the CON group, the relative abundance of Proteobacteria and Bacteroides in the Treatment group was similar to that in the CON group. At the genus level, the relative abundance of
in the Case group was significantly increased, accompanied by a significant decrease in the relative abundance of
, and the relative abundance of
and
in Treatment group was similar to that in the CON group. Moreover, the fluorobenzoate degradation pathway (KO00364) was significantly increased in the Case group, while this pathway was significantly decreased in the Treatment group. In conclusion, MBZYQD can improve the immune function of the host by regulating the diversity, structure and function of the intestinal microbiota to treat myasthenia gravis.
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