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1.
Copper (Cu) offers a means for producing value‐added fuels through the electrochemical reduction of carbon dioxide (CO2), i.e., the CO2 reduction reaction (CO2RR), but designing Cu catalysts with significant Faradaic efficiency to C2+ products remains as a great challenge. This work demonstrates that the high activity and selectivity of Cu to C2+ products can be achieved by atomic‐scale spacings between two facets of Cu particles. These spacings are created by lithiating CuOx particles, removing lithium oxides formed, and electrochemically reducing CuOx to metallic Cu. Also, the range of spacing (ds) is confirmed via the 3D tomographs using the Cs‐corrected scanning transmission electron microscopy (3D tomo‐STEM), and the operando X‐ray absorption spectra show that oxidized Cu reduces to the metallic state during the CO2RR. Moreover, control of ds to 5–6 Å allows a current density exceeding that of unmodified CuOx nanoparticles by about 12 folds and a Faradaic efficiency of ≈80% to C2+. Density functional theory calculations support that ds of 5–6 Å maximizes the binding energies of CO2 reduction intermediates and promotes C–C coupling reactions. Consequently, this study suggests that control of ds can be used to realize the high activity and C2+ product selectivity for the CO2RR.  相似文献   

2.
CO2 electrochemical reduction (CO2RR) can mitigate environmental issues while providing valuable products, yet challenging in activity, selectivity, and stability. Here, a CuS-Bi2S3 heterojunction precursor is reported that can in situ reconstruct to Cu-doped Bismuth (CDB) electrocatalyst during CO2RR. The CDB exhibits an industrial-compatible current density of −1.1 A cm−2 and a record-high formate formation rate of 21.0 mmol h−1 cm−2 at −0.86 V versus the reversible hydrogen electrode toward CO2RR to formate, dramatically outperforming currently reported catalysts. Importantly, the ultrawide potential region of 1050 mV with high formate Faradaic efficiency of over 90% and superior long-term stability for more than 100 h at −400 mA cm−2 can also be realized. Experimental and theoretical studies reveal that the remarkable CO2RR performance of CDB results from the doping effect of Cu which optimizes adsorption of the *OCHO and boosts the structural stability of metallic bismuth catalyst. This study provides valuable inspiration for the design of element-doping electrocatalysts to enhance catalytic activity and durability.  相似文献   

3.
Elevated atmospheric CO2 concentration ([CO2]) generally enhances C3 plant productivity, whereas acute heat stress, which occurs during heat waves, generally elicits the opposite response. However, little is known about the interaction of these two variables, especially during key reproductive phases in important temperate food crops, such as soybean (Glycine max). Here, we grew soybean under elevated [CO2] and imposed high‐ (+9°C) and low‐ (+5°C) intensity heat waves during key temperature‐sensitive reproductive stages (R1, flowering; R5, pod‐filling) to determine how elevated [CO2] will interact with heat waves to influence soybean yield. High‐intensity heat waves, which resulted in canopy temperatures that exceeded optimal growth temperatures for soybean, reduced yield compared to ambient conditions even under elevated [CO2]. This was largely due to heat stress on reproductive processes, especially during R5. Low‐intensity heat waves did not affect yields when applied during R1 but increased yields when applied during R5 likely due to relatively lower canopy temperatures and higher soil moisture, which uncoupled the negative effects of heating on cellular‐ and leaf‐level processes from plant‐level carbon assimilation. Modeling soybean yields based on carbon assimilation alone underestimated yield loss with high‐intensity heat waves and overestimated yield loss with low‐intensity heat waves, thus supporting the influence of direct heat stress on reproductive processes in determining yield. These results have implications for rain‐fed cropping systems and point toward a climatic tipping point for soybean yield when future heat waves exceed optimum temperature.  相似文献   

4.
Electrochemical CO2 reduction (CO2RR) is a promising technology to produce value‐added fuels and weaken the greenhouse effect. Plenty of efforts are devoted to exploring high‐efficiency electrocatalysts to tackle the issues that show poor intrinsic activity, low selectivity for target products, and short‐lived durability. Herein, density functional theory calculations are firstly utilized to demonstrate guidelines for design principles of electrocatalyst, maximum exposure of catalytic active sites for MoS2 edges, and electron transfer from N‐doped carbon (NC) to MoS2 edges. Based on the guidelines, a hierarchical hollow electrocatalyst comprised of edge‐exposed 2H MoS2 hybridized with NC for CO2RR is constructed. In situ atomic‐scale observation for catalyst growth is performed by using a specialized Si/SiNx nanochip at a continuous temperature‐rise period, which reveals the growth mechanism. Abundant exposed edges of MoS2 provide a large quantity of active centers, which leads to a low onset potential of ≈40 mV and a remarkable CO production rate of 34.31 mA cm?2 with 92.68% of Faradaic efficiency at an overpotential of 590 mV. The long‐term stability shows negligible degradation for more than 24 h. This work provides fascinating insights into the construction of catalysts for efficient CO2RR.  相似文献   

5.
Carbon dioxide (CO2) is one of the end products of fuel combustion and the major component of the greenhouse gases. The reduction of atmospheric CO2 not only decreases environmental pollution but also produces value‐added chemicals, solving energy and environment issues simultaneously. One significant challenge is the low conversion efficiency of CO2 reduction due to the inertness of the CO2 molecule. The design of the catalyst nanomaterials with the high selectivity, stability, and the activation capabilities for the conversion of CO2 is needed. Atomic layer deposition (ALD), capable of constructing catalysts with atomic‐level precision in a highly controllable manner, is a promising technique to address the key problems in CO2 reduction. This review explores the application of ALD in CO2 reduction, emphasizing the designs of the efficient catalyst nanomaterials fabricated by the ALD technique and their applications in CO2 reduction and capture. The significance of the ALD catalysts with the fine structures is highlighted to obtain a better understanding of the catalytic performance–aimed benefits as well as an outlook on the ALD‐designed catalysts for the reduction of CO2.  相似文献   

6.
Renewable-electricity-powered electrochemical CO2 reduction (CO2RR) is considered one of the most promising ways to convert exhaust CO2 into value-added chemicals and fuels. Among various CO2RR products, CO is of great significance since it can be directly used as feedstock to produce chemical products through the Fischer–Tropsch process. However, the CO2-to-CO electrocatalytic process is often accompanied by a kinetically competing side reaction: H2 evolution reaction (HER). Designing electrocatalysts with tunable electronic structures is an attractive strategy to enhance CO selectivity. In this work, a CeNCl-CeO2 heterojunction-modified Ni catalyst is successfully synthesized with high CO2RR catalytic performance by the impregnation-calcination method. Benefiting from the strong electron interaction between the CeNCl-CeO2 heterojunction and Ni nanoparticles (NPs), the catalytic performance is greatly improved. Maximal CO Faradaic efficiency (FE) is up to 90% at −0.8 V (vs RHE), plus good stability close to 12 h. Detailed electrochemical tests and density functional theory (DFT) calculation results reveal that the introduction of the CeNCl-CeO2 heterojunction tunes the electronic structure of Ni NPs. The positively charged Ni center leads to an enhanced local electronic structure, thus promoting the activation of CO2 and the adsorption of *COOH.  相似文献   

7.
An innovative use of a thermoelectric material (BiCuSeO) as a support and promoter of catalysis for CO2 hydrogenation is reported here. It is proposed that the capability of thermoelectric materials to shift the Fermi level and work function of a catalyst lead to an exponential increase of catalytic activity for catalyst particles deposited on its surface. Experimental results show that the CO2 conversion and CO selectivity are increased significantly by a thermoelectric Seebeck voltage. This suggests that the thermoelectric effect can not only increase the reaction rate but also change chemical equilibrium, which leads to the change of thermodynamic equilibrium for the conversion of CO2 in its hydrogenation reactions. It is also shown that this thermoelectric promotion of catalysis enables BiCuSeO oxide itself to have a high catalytic activity for CO2 hydrogenation. The generic nature of the mechanism suggests the possibility that many catalytic chemical reactions can be tuned in situ to achieve much higher reaction rates, or at lower temperatures, or have better desired selectivity through changing the backside temperature of the thermoelectric support.  相似文献   

8.
A copper‐oxide‐based catalyst enriched with paramelaconite (Cu4O3) is presented and investigated as an electrocatalyst for facilitating electroreduction of CO2 to ethylene and other hydrocarbons. Cu4O3 is a member of the copper‐oxide family and possesses an intriguing mixed‐valance nature, incorporating an equal number of Cu+ and Cu2+ ions in its crystal structure. The material is synthesized using a solvothermal synthesis route and its structure is confirmed via powder X‐ray diffraction, transmission electron microscope based selected area electron diffraction, and X‐ray photoelectron spectroscopy. A flow reactor equipped with a gas diffusion electrode is utilized to test a copper‐based catalyst enriched with the Cu4O3 phase under CO2 reduction conditions. The Cu4O3‐rich catalyst (PrC) shows a Faradaic efficiency for ethylene over 40% at 400 mA cm?2. At ?0.64 versus reversible hydrogen electrode, the highest C2+/C1 product ratio of 4.8 is achieved, with C2+ Faradaic efficiency over 61%. Additionally, the catalyst exhibits a stable performance for 24 h at a constant current density of 200 mA cm?2.  相似文献   

9.
A photoautotrophic soybean suspension culture (SB-P) was used to study CO2 assimilation while exposed to elevated or ambient CO2 levels. These studies showed that under elevated CO2 (5% v/v) malate is the dominant fixation product, strongly suggesting that phosphoenolpyruvate carboxylase (PEPCase) is the primary enzyme involved in carbon fixation in these cells under their normal growth conditions. Citrate and [aspartate + glutamate] were also significant fixation products during fifteen minutes of exposure to 14CO2. During the ten minute unlabeled CO2 chase however, 14C-malate continued to increase while citrate and [aspartate + glutamate] declined. Fixation of 14CO2 under ambient CO2 levels (0.037%) showed a very different product pattern as 3-phosphoglycerate was very high in the first one to two minutes followed by increases in [serine + glycine] and [aspartate + glutamate]. Hexose phosphates were also quite high initially but then declined relatively rapidly. Thus, the carbon fixation pattern at ambient CO2 levels resembles somewhat that seen in C3 leaf cells while that seen at elevated CO2 levels more closely resembles that of a C4 plant. The initial fixation product of C3 plants, 3-PGA, was never detectable under high CO2 conditions. These data suggest that an in vitro photoautotrophic system would be suitable for studying carbon fixation physiology during photosynthetic and non-photosynthetic growth.Abbreviations SB-P photoautotrophic soybean cells - PEPCase phosphoenol-pyruvate carboxylase - RuBPCase ribulose bisphosphate carboxylase/oxygenase - 3-PGA 3-phosphoglycerate  相似文献   

10.
The C3 pathways of CO2 reduction reaction (CO2RR) lead to the generation of high-value-added chemicals for broad industrial applications, which are still challenging for current electrocatalysis. Only limited electrocatalysts have been reported with the ability to achieve C3 products while the corresponding reaction mechanisms are highly unclear. To overcome such challenges, the first-principle machine learning (FPML) technique on graphdiyne-based atomic catalysts (GDY-ACs) is introduced to directly predict the reaction trends for the key C─C─C coupling processes and the conversions to different C3 products for the first time. All the prediction results are obtained only based on the learning dataset constructed by density functional theory (DFT) calculation results for C1 and C2 pathways, offering an efficient approach to screen promising electrocatalyst candidates for varied C3 products. More importantly, the ML predictions not only reveal the significant role of the neighboring effect and the small–large integrated cycle mechanisms but also supply important insights into the C─C─C coupling processes for understanding the competitive reactions among C1 to C3 pathways. This work has offered an advanced breakthrough for the complicated CO2RR processes, accelerating the future design of novel ACs for C3 products with high efficiency and selectivity.  相似文献   

11.
The production of small quantities of monoclonal antibodies and recombinant proteins was carried out using a new low cost production system, the Super Spinner. Into a 1 1 standard Duran® flask a membrane stirrer equipped with a polypropylene hollow fiber membrane was installed to improve the oxygen supply by bubble-free aeration. The aeration was facilitated by using the CO2 conditioned incubator gas, which was pumped through the membrane stirrer via a small membrane pump. The maximal oxygen transfer rate (OTRmax) of the Super Spinner was detected. For this purpose one spinner flask was equipped with an oxygen electrode. The OTRmax was measured by the dynamic method. The ratio of membrane length to culture volume was adapted corresponding to the oxygen uptake rate of the cells according to the desired cell density. A balanced nutrient supply resulted in an optimal formation and yield of products.  相似文献   

12.
The photoelectrochemical CO2 reduction reaction (photo-CO2RR) is a promising technology to convert CO2 into high-value-added carbon-based chemicals using a relatively low voltage, which can economically solve the problem of CO2 emissions. Nevertheless, unlike the conventional electrochemical CO2RR approach, photo-CO2RR technology is in its initial development stage. Particularly, when sunlight is applied to photoelectrodes for photo-CO2RR, severe photocorrosion is unavoidable, resulting in the deterioration of fundamental functions including device long-term stability and conversion performance. This study proposes an innovative two-step catalyst formation strategy to enable the efficient photo-CO2RR with Cu catalysts prepared using intrinsic photocorrosion of the Cu2O absorption layer. This approach is based on the harmonized process design of the i) growth of physically generated Cu nanoparticles and ii) construction of improved photoelectrochemical Cu cluster catalysts. The vacuum-evaporated Cu seeds are designed to induce an evenly dispersed electrical path on Cu2O, and the selectively concentrated electrical field from the Cu seeds provides preferential sites for metallic Cu catalysts in subsequent photoelectrochemical reduction. This harmonized combination process of Cu catalysts on Cu2O demonstrates a synergistic performance of −1.2 mA cm−2 at 0 VRHE with suppression of photocorrosion and produces ≈95% CO product gas (0.4 VRHE).  相似文献   

13.
14.
Rational design of electrocatalysts toward efficient CO2 electroreduction has the potential to reduce carbon emission and produce value‐added chemicals. In this work, a strategy of constructing 2D confined‐space as molecular reactors for enhanced electrocatalytic CO2 reduction selectivity is demonstrated. Highly ordered 2D nanosheet lamella assemblies are achieved via weak molecular interaction of atomically thin titania nanosheets, a variety of cationic surfactants, and SnO2 nanoparticles. The interlayer spacings can be tuned from 0.9 to 3.0 nm by using different surfactant molecules. These 2D assemblies of confined‐space catalysts exhibit a strong size dependence of CO2 electroreduction selectivity, with a peak Faradaic efficiency of 73% for formate production and excellent electrochemical stability at an optimal interspacing of ≈2.0 nm. This work suggests great potential for constructing new molecular‐size reactors, for highly selective electrocatalytic CO2 reduction.  相似文献   

15.
Replacing oxygen (O2) with air is a critical step in the development of lithium (Li)–air batteries. A trace amount of carbon dioxide (CO2) in the air is, however, influentially involved in the O2 chemistry, which indicates that a fundamental understanding of the effect of CO2 is required for the design of practical cells. When up to 30% CO2 is added to Li–O2 cells, CO2 acts as an O2? scavenger. Their chemical reactions form soluble products, CO42? and C2O62?, in the tetraglyme electrolyte solution, and enhance full capacity and cell cyclability. A critical challenge is, however, the sluggish decomposition of the coproduct Li2CO3 during recharge. To lower the charging overpotential, a Br3?/Br2 redox couple is incorporated and its redox behavior is investigated using spectroscopic methods. The redox shuttle of Br3?/Br2 decomposes amorphous Li2CO3 more efficiently than its crystalline counterpart. It is revealed that Br2 combines with Br3? to form a Br2···Br3? complex, which acts as a mobile catalyst in the electrolyte solution without swift precipitation of the nonpolar Br2. This comprehensive study, revealing the molecular structure and redox process of mobile catalysts, provides an insight into improving the design of redox couples toward superior cycling performance.  相似文献   

16.
Free‐air CO2 enrichment (FACE) allows open‐air elevation of [CO2] without altering the microclimate. Its scale uniquely supports simultaneous study from physiology and yield to soil processes and disease. In 2005 we summarized results of then 28 published observations by meta‐analysis. Subsequent studies have combined FACE with temperature, drought, ozone, and nitrogen treatments. Here, we summarize the results of now almost 250 observations, spanning 14 sites and five continents. Across 186 independent studies of 18 C3 crops, elevation of [CO2] by ca. 200 ppm caused a ca. 18% increase in yield under non‐stress conditions. Legumes and root crops showed a greater increase and cereals less. Nitrogen deficiency reduced the average increase to 10%, as did warming by ca. 2°C. Two conclusions of the 2005 analysis were that C4 crops would not be more productive in elevated [CO2], except under drought, and that yield responses of C3 crops were diminished by nitrogen deficiency and wet conditions. Both stand the test of time. Further studies of maize and sorghum showed no yield increase, except in drought, while soybean productivity was negatively affected by early growing season wet conditions. Subsequent study showed reduced levels of nutrients, notably Zn and Fe in most crops, and lower nitrogen and protein in the seeds of non‐leguminous crops. Testing across crop germplasm revealed sufficient variation to maintain nutrient content under rising [CO2]. A strong correlation of yield response under elevated [CO2] to genetic yield potential in both rice and soybean was observed. Rice cultivars with the highest yield potential showed a 35% yield increase in elevated [CO2] compared to an average of 14%. Future FACE experiments have the potential to develop cultivars and management strategies for co‐promoting sustainability and productivity under future elevated [CO2].  相似文献   

17.
Direct ethanol fuel cells (DEFCs) have great activity as a green energy conversion device. However, the weak activity of most anode electrocatalysts for the C? C bond cleavage is an obstacle to the DEFCs development. Herein, a simple galvanic replacement reaction strategy to synthesize hollow and porous PtRhCu trimetallic nanoboxes (CNBs) with a tunable Pt/Rh atomic ratio is developed. For the ethanol oxidation reaction (EOR), PtRhCu CNBs show morphology and composition‐dependent electrocatalytic activity. The composition optimized Pt54Rh4Cu42 CNBs exhibit excellent specific and mass activity and stability for the EOR, which is attributed to its unique geometric structure and synergistic effects. The hollow porous structure can effectively enhance the atomic utilization and mass transfer. The introduction of Cu improves the antipoisoning capability for CO. The introduction of Rh elevates the self‐stability of PtRhCu CNBs. More importantly, further electrochemical results confirm that the introduction of Rh significantly promotes the cleavage of C? C bonds, leading to the transformation of the main catalytic pathway for EOR from C2 to C1 pathway. The real concentration detection for C2 products (CH3COOH and CH3CHO) shows Pt54Rh4Cu42 CNBs have a nearly 11.5‐fold C1 pathway enhancement compared to Pt nanoparticles, showing an obvious selectivity enhancement for the C1 pathway.  相似文献   

18.
Xu Y  Ye TQ  Qiu SB  Ning S  Gong FY  Liu Y  Li QX 《Bioresource technology》2011,102(10):6239-6245
A novel approach for high efficient conversion of the CO2-rich bio-syngas into the CO-rich bio-syngas was carried out by using biomass char and Ni/Al2O3 catalyst, which was successfully applied for production of bio-methanol from bio-oil. After the bio-syngas conditioning, the CO2/CO ratio prominently dropped from 6.33 to 0.01-0.28. The maximum CO yield in the bio-syngas conditioning process reached about 1.96 mol/(mol CO2) with a nearly complete conversion of CO2 (99.5%). The performance of bio-methanol synthesis was significantly improved via the conditioned bio-syngas, giving a maximum methanol yield of 1.32 kg/(kgcatalyst h) with a methanol selectivity of 99%. Main reaction paths involved in the bio-syngas conditioning process have been investigated in detail by using different model mixture gases and different carbon sources.  相似文献   

19.
The nature of photosynthetic acclimation to elevated CO2 is evaluated from the results of over 40 studies focusing on the effect of long-term CO2 enrichment on the short-term response of photosynthesis to intercellular CO2 (the A/Ci response). The effect of CO2 enrichment on the A/Ci response was dependent on growth conditions, with plants grown in small pots (< 5 L) or low nutrients usually exhibiting a reduction of A at a given Ci, while plants grown without nutrient deficiency in large pots or in the field tended to exhibit either little reduction or an enhancement of A at a given Ci following a doubling or tripling of atmospheric CO2 during growth. Using theoretical interpretations of A/Ci curves to assess acclimation, it was found that when pot size or nutrient deficiency was not a factor, changes in the shape of A/Ci curves which are indicative of a reallocation of resources within the photosynthetic apparatus typically were not observed. Long-term CO2 enrichment usually had little effect or increased the value of A at all Ci. However, a minority of species grown at elevated CO2 exhibited gas exchange responses indicative of a reduced amount of Rubisco and an enhanced capacity to metabolize photosynthetic products. This type of response was considered beneficial because it enhanced both photosynthetic capacity at high CO2 and reduced resource investment in excessive Rubisco capacity. The ratio of intercellular to ambient CO2 (the Ci/Ca ratio) was used to evaluate stomatal acclimation. Except under water and humidity stress, Ci/Ca exhibited no consistent change in a variety of C3 species, indicating no stomatal acclimation. Under drought or humidity stress, Ci/Ca declined in high-CO2 grown plants, indicating stomata will become more conservative during stress episodes in future high CO2 environments.Abbreviations A net CO2 assimilation rate - Ci (Ca) intercellular (ambient) partial pressure of CO2 - operational Ci intercellular partial pressure of CO2 at a given ambient partial pressure of CO2 - gs stomatal conductance - normal CO2 current atmospheric mole fraction of CO2 (330 to 355 mol mol–1) - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase  相似文献   

20.
Electrochemical reduction of carbon dioxide (CO2) typically suffers from low selectivity and poor reaction rates that necessitate high overpotentials, which impede its possible application for CO2 capture, sequestration, or carbon‐based fuel production. New strategies to address these issues include the utilization of photoexcited charge carriers to overcome activation barriers for reactions that produce desirable products. This study demonstrates surface‐plasmon‐enhanced photoelectrochemical reduction of CO2 and nitrate (NO3?) on silver nanostructured electrodes. The observed photocurrent likely originates from a resonant charge transfer between the photogenerated plasmonic hot electrons and the lowest unoccupied molecular orbital (MO) acceptor energy levels of adsorbed CO2, NO3?, or their reductive intermediates. The observed differences in the resonant effects at the Ag electrode with respect to electrode potential and photon energy for CO2 versus NO3? reduction suggest that plasmonic hot‐carriers interact selectively with specific MO acceptor energy levels of adsorbed surface species such as CO2, NO3?, or their reductive intermediates. This unique plasmon‐assisted charge generation and transfer mechanism can be used to increase yield, efficiency, and selectivity of various photoelectrochemical processes.  相似文献   

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