ABSTRACT
Tandem catalysis provides an economical and energy-efficient process for the production of fine chemicals. In this work, we demonstrate that a rationally synthesized carbon-based catalyst with atomically dispersed dual Fe-Al sites (ADD-Fe-Al) achieves superior catalytic activity for the one-pot oxidative carboxylation of olefins (conversion â¼97%, selectivity â¼91%), where the yield of target product over ADD-Fe-Al is at least 62% higher than that of monometallic counterparts. The kinetic results reveal that the excellent catalytic performance arises from the synergistic effect between Fe (oxidation site) and Al sites (cycloaddition site), where the efficient CO2 cycloaddition with epoxides in the presence of Al sites (3.91 wt %) positively shifts the oxidation equilibrium to olefin epoxidation over Fe sites (0.89 wt %). This work not only offers an advanced catalyst for oxidative carboxylation of olefins but also opens up an avenue for the rational design of multifunctional catalysts for tandem catalytic reactions in the future.
ABSTRACT
The Free Air CO2 Enrichment (FACE) facility enables the study of plant responses to climate change under open field conditions. This meta-analysis was conducted to quantitatively assess the effects of elevated CO2 concentration ([CO2]) on 47 variables describing rice growth physiology and whether CO2 effects were influenced by cultivar, plant growth stage, nitrogen application rate or temperature. On average, elevated [CO2] increased root and shoot biomass by 28% and 19%, respectively. Among shoot organs, the [CO2]-induced increase in leaf biomass was only 9%, significantly smaller than a 24% increase in stems or a 25% increase in panicles. The higher biomass for FACE rice was consistent with the stimulation in plant height (4%), maximum tiller number (11%), leaf area index (9%) and light-saturated photosynthetic rate (Asat, 22%). When compared within rice groups, hybrid rice showed the greatest CO2 response in growth and leaf physiological variables. Elevated [CO2] increased plant biomass and Asat at each rice growth stage, but the increment tended to decline with the advancement of rice growth and development. The increase in aboveground biomass at elevated [CO2] was enhanced by a higher nitrogen supply but reduced with a temperature elevation of 1-2 °C. Rice growth benefited more from elevated [CO2] in Chinese FACE studies than in Japanese FACE studies, which may result from the different cultivars and nitrogen application rates used in the two countries. Combined with a previous meta-analysis of the rice yield response to FACE, the [CO2] level predicted in the middle of this century will improve rice productivity by stimulating leaf photosynthesis. However, the effects of CO2 on the photosynthetic rate and rice growth tend to shrink over the plant life cycle. Selecting heat-resistant, high-yield hybrid rice cultivars with large sink capacity, supplemented with appropriate nitrogen input, will maximize the CO2 fertilizer effect in the future.
Subject(s)
Oryza , Carbon Dioxide , Plant LeavesABSTRACT
Exploiting environmentally friendly and robust electrocatalysts for overall water splitting is of utmost importance in order to alleviate the excessive global energy consumption and climate change. Herein, a simple phosphoselenization method was used to prepare Co2P and CoSe2 coupled nanosheet and nanoneedle composite materials on nickel foam (Co2P/CoSe2/NF). Density functional theory calculations showed that Co2P had a higher water adsorption energy compared with CoSe2, indicating that H2O molecules are strongly adsorbed on the active sites of Co2P, which speeds up the kinetic process of water splitting. The Co2P/CoSe2-300 material displayed superior electrocatalytic activity for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline medium. It's worth noting that the Co2P/CoSe2-300 composite material nanoarrays merely needed an ultralow overpotential of 280 mV to drive a current intensity of 100 mA cm-2 for OER. In addition, when a two-electrode system was constructed for overall water splitting, the current intensity of 20 mA cm-2 could be reached while requiring an ultrasmall cell voltage of 1.52 V, which is one of the best catalytic activities reported up to now. Experimental and density functional theory calculations showed that the superior electrocatalytic performance of Co2P/CoSe2-300 could be attributed to its higher electron-transfer rate, higher water adsorption energy, and the synergistic effect of Co2P and CoSe2. Our work provides a novel approach for the one-step construction of composite materials as environmentally friendly and inexpensive water splitting catalysts.