Electrocatalytic Reduction of Gaseous CO2 to CO on Sn/Cu‐Nanofiber‐Based Gas Diffusion Electrodes

Earth‐abundant Sn/Cu catalysts are highly selective for the electrocatalytic reduction of CO₂ to CO in aqueous electrolytes. However, CO₂ mass transport limitations, resulting from the low solubility of CO₂ in water, so far limit the CO partial current density for Sn/Cu catalysts to about 10 mA cm^?2. Here, a freestanding gas diffusion electrode design based on Sn‐decorated Cu‐coated electrospun polyvinylidene fluoride nanofibers is demonstrated. The use of gaseous CO₂ as a feedstock alleviates mass transport limitations, resulting in high CO partial current densities above 100 mA cm^?2, while maintaining high CO faradaic efficiencies above 80%. These results represent an important step toward an economically viable pathway to CO₂ reduction.     

Formation of Au(III)-DNA Coordinate Complex by Laser Ablation of Au Nanoparticles in Solution

We discovered that an Au(III)-DNA coordinate complex, Au(III)(DNA-base)₂(amine)l, are formed by laser ablation of Au nanoparticles in an aqueous solution containing DNA molecules in the presence of amines and multi-valent cations, where l represents an unknown ligand (either amine or water). Optical absorption spectrum of the solution after laser ablation exhibited a 360 nm absorption peak assigned to ligand→Au(III) charge transfer (LMCT) band of the coordinate complex. The complex is considered to be formed as follows: 1) the DNA molecules are neutralized by binding the multi-valent cations to their negatively charged phosphate groups, and adsorbed on the surface of the Au nanoparticles by a hydrophobic interaction, 2) Au(III) ions are liberated from the Au nanoparticles by laser ablation, and 3) an Au(III) ion reacts with amine and two DNA bases of a DNA molecule into an Au(III)(DNA-base)₂(amine)l.     

Nanoporous Au Thin Films on Si Photoelectrodes for Selective and Efficient Photoelectrochemical CO2 Reduction

An Si photoelectrode with a nanoporous Au thin film for highly selective and efficient photoelectrochemical (PEC) CO₂ reduction reaction (CO₂RR) is presented. The nanoporous Au thin film is formed by electrochemical reduction of an anodized Au thin film. The electrochemical treatments of the Au thin film critically improve CO₂ reduction catalytic activity of Au catalysts and exhibit CO Faradaic efficiency of 96% at 480 mV of overpotential. To apply the electrochemical pretreatment of Au films for PEC CO₂RR, a new Si photoelectrode design with mesh‐type co‐catalysts independently wired at the front and the back of the photoelectrode is demonstrated. Due to the superior CO₂RR activity of the nanoporous Au mesh and high photovoltage from Si, the Si photoelectrode with the nanoporous Au thin film mesh shows conversion of CO₂ to CO with 91% Faradaic efficiency at positive potential than the CO₂/CO equilibrium potential.     

Synthesis of Large Surface‐Area g‐C3N4 Comodified with MnOx and Au‐TiO2 as Efficient Visible‐Light Photocatalysts for Fuel Production

Herein, this study successfully fabricates porous g‐C₃N₄‐based nanocomposites by decorating sheet‐like nanostructured MnO_x and subsequently coupling Au‐modified nanocrystalline TiO₂. It is clearly demonstrated that the as‐prepared amount‐optimized nanocomposite exhibits exceptional visible‐light photocatalytic activities for CO₂ conversion to CH₄ and for H₂ evolution, respectively by ≈28‐time (140 µmol g^?1 h^?1) and ≈31‐time (313 µmol g^?1 h^?1) enhancement compared to the widely accepted outstanding g‐C₃N₄ prepared with urea as the raw material, along with the calculated quantum efficiencies of ≈4.92% and 2.78% at 420 nm wavelength. It is confirmed mainly based on the steady‐state surface photovoltage spectra, transient‐state surface photovoltage responses, fluorescence spectra related to the produced ?OH amount, and electrochemical reduction curves that the exceptional photoactivities are comprehensively attributed to the large surface area (85.5 m² g^?1) due to the porous structure, to the greatly enhanced charge separation and to the introduced catalytic functions to the carrier‐related redox reactions by decorating MnO_x and coupling Au‐TiO₂, respectively, to modulate holes and electrons. Moreover, it is suggested mainly based on the photocatalytic experiments of CO₂ reduction with isotope ¹³CO₂ and D₂O that the produced ?CO₂ and ?H as active radicals would be dominant to initiate the conversion of CO₂ to CH₄.     

Shape‐Controlled CO2 Electrochemical Reduction on Nanosized Pd Hydride Cubes and Octahedra

Electrochemical CO₂ reduction reaction (CO₂RR) provides a potential pathway to mitigate challenges related to CO₂ emissions. Pd nanoparticles have shown interesting properties as CO₂RR electrocatalysts, while how different facets of Pd affect its performance in CO₂ reduction to synthesis gas with controlled H₂ to CO ratios has not been understood. Herein, nanosized Pd cubes and octahedra particles dominated by Pd(100) and Pd(111) facets are, respectively, synthesized. The Pd octahedra particles show higher CO selectivity (up to 95%) and better activity than Pd cubes and commercial particles. For both Pd octahedra and cubes, the ratio of H₂/CO products is tunable between 1 and 2, a desirable ratio for methanol synthesis and the Fischer–Tropsch processes. Further studies of Pd octahedra in a 25 cm² flow cell show that a total CO current of 5.47 A is achieved at a potential of 3.4 V, corresponding to a CO partial current density of 220 mA cm^?2. In situ X‐ray absorption spectroscopy studies show that regardless of facet Pd is transformed into Pd hydride (PdH) under reaction conditions. Density functional theory calculations show that the reduced binding energies of CO and HOCO intermediates on PdH(111) are key parameters to the high current density and Faradaic efficiency in CO₂ to CO conversion.     

In deep shade, elevated CO2 increases the vigor of tropical climbing plants

Climbing plants have profound influences on tropical forest dynamics and may take particular advantage from atmospheric CO₂ enrichment, thus potentially enhancing tree turnover. Here we test the effect of a four‐step CO₂‐enrichment on growth of three typical Yucatan (Mexico) climbers, across two low photon flux densities, representing typical understory situations. In pairs of two, species of Gonolobus (Asclepiadaceae), Ceratophytum (Bignoniaceae) and Thinouia (Sapindaceae) were grown on Yucatan forest soil in growth cabinets, which simulated the diurnal climate variation. Biomass increased non‐linearly in response to CO₂ enrichment from 280 (preindustrial) to 420 ppm and 560 ppm, but then (700 ppm) leveled off. The relative effect of CO₂‐enrichment between the two lower (280–420 ppm) CO₂ concentrations was 63% at low light (LL == 42 µmol m^2?2 s^2?1), compared to 37% at high light (HL = 87 µmol m^2?2 s^2?1). This overall response of species pairs was the combined effect of linear and non‐linear responses of the individual species across CO₂ treatments. Plant biomass was 61% larger in HL compared to LL. The species‐specific response depended on the neighbor, a species grew with h, irrespective of plant size. Stem length increased, but not consistently across species and light conditions. Specific stem length (SSL, length per dry mass) declined non‐linearly in all three species as CO₂ concentration increased (more pronounced at LL than at HL). SLA (leaf area per unit leaf dry mass) became lower as CO₂ concentration increased (more pronounced in HL). Enhanced vigor of climbers under elevated CO₂ as documented here may accelerate tropical forest dynamics and lead to greater abundance of early succesional tree species. This could reduce forest carbon stocking in the long run.     

Overpotentials and Faraday Efficiencies in CO2 Electrocatalysis–the Impact of 1‐Ethyl‐3‐Methylimidazolium Trifluoromethanesulfonate

The mixtures of room temperature ionic liquid 1‐ethyl‐3‐methylimidazolium trifluoromethanesulfonate ([EMIM]TFO) and water as electrolytes for reduction of CO₂ to CO are reported. Linear sweep voltammetry shows overpotentials for CO₂ reduction and the competing hydrogen evolution reaction (HER), both of which vary as a function of [EMIM]TFO concentration in the range from 4 × 10^?3m (0.006 mol%) to 4869 × 10^?3m (50 mol%). A steady lowering of overpotentials up to an optimum for 334 × 10?³m is identified. At 20 mol% and more of [EMIM]TFO, a significant CO₂ reduction plateau and inhibition of HER, which is limited by H₂O diffusion, is noted. Such a plateau in CO₂ reduction correlates to high CO Faraday efficiencies. In case of 50 mol% [EMIM]TFO, a broad plateau spanning over a potential range of 0.58 V evolves. At the same time, the overpotential for HER is increased by 1.20 V when compared to 334 × 10^?3m and, in turn, HER is largely inhibited. The Faraday efficiencies for CO and H₂ formation feature 95.6% ± 6.8% and 0.5% ± 0.3%, respectively, over a period of 3 h in a separator divided cell. Cathodic as well as anodic electrochemical stability of the electrolyte throughout this time period is corroborated in ¹H NMR spectroscopic measurements.     

Exploiting Synergistic Effect by Integrating Ruthenium–Copper Nanoparticles Highly Co‐Dispersed on Graphene as Efficient Air Cathodes for Li–CO2 Batteries

Li–CO₂ batteries are attractive electrical energy storage devices; however, they still suffer from unsatisfactory electrochemical performance, and the kinetics of CO₂ reduction and evolution reactions must be improved significantly. Herein, a composite of ruthenium–copper nanoparticles highly co‐dispersed on graphene (Ru–Cu–G) as efficient air cathodes for Li–CO₂ batteries is designed. The Li–CO₂ batteries with Ru–Cu–G cathodes exhibit ultra‐low overpotential and can be operated for 100 cycles with a fixed capacity of 1000 mAh g^?1 at 200 and 400 mA g^?1. The synergistic effect between Ru and Cu not only regulates the growth of discharge products, but also promotes CO₂ reduction and evolution reactions by changing the electron cloud density of the surface between Ru and Cu. This work may provide new directions and strategies for developing highly efficient air cathodes for Li–CO₂ batteries, or even practical Li–air batteries.     

Activation of Ni Particles into Single Ni–N Atoms for Efficient Electrochemical Reduction of CO2

Electrochemical reduction of carbon dioxide (CO₂) to fuels and value‐added industrial chemicals is a promising strategy for keeping a healthy balance between energy supply and net carbon emissions. Here, the facile transformation of residual Ni particle catalysts in carbon nanotubes into thermally stable single Ni atoms with a possible NiN₃ moiety is reported, surrounded with a porous N‐doped carbon sheath through a one‐step nanoconfined pyrolysis strategy. These structural changes are confirmed by X‐ray absorption fine structure analysis and density functional theory (DFT) calculations. The dispersed Ni single atoms facilitate highly efficient electrocatalytic CO₂ reduction at low overpotentials to yield CO, providing a CO faradaic efficiency exceeding 90%, turnover frequency approaching 12 000 h^?1, and metal mass activity reaching about 10 600 mA mg^?1, outperforming current state‐of‐the‐art single atom catalysts for CO₂ reduction to CO. DFT calculations suggest that the Ni@N₃ (pyrrolic) site favors *COOH formation with lower free energy than Ni@N₄, in addition to exothermic CO desorption, hence enhancing electrocatalytic CO₂ conversion. This finding provides a simple, scalable, and promising route for the preparation of low‐cost, abundant, and highly active single atom catalysts, benefiting future practical CO₂ electrolysis.     

Ni–Fe–La(Sr)Fe(Mn)O3 as a New Active Cermet Cathode for Intermediate‐Temperature CO2 Electrolysis Using a LaGaO3‐Based Electrolyte

Various additives to Ni–Fe systems are studied as cermet cathodes for CO₂ electrolysis (973–1173 K) using a La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ (LSGM) electrolyte, which is one of the most promising oxide‐ion conductors for intermediate‐temperature solid‐oxide electrolysis cells in terms of ionic‐transport number and conductivity. It is found that Ni–Fe–La_0.6Sr_0.4Fe_0.8Mn_0.2O₃ (Ni–Fe–LSFM) exhibits a remarkable performance with a current density of 2.32 A cm^?2 at 1.6 V and 1073 K. The cathodic overpotential is significantly decreased by mixing the LSFM powder with Ni–Fe, which is related to the increase in the number of reaction sites for CO₂ reduction. For Ni–Fe–LSFM, much smaller particles (<200 nm) are sustained under CO₂ electrolysis conditions at high temperatures than for Ni–Fe. X‐ray diffraction analysis suggests that the main phases of Ni–Fe–LSFM are Ni and LaFeO₃; thus, the oxide phase of LaFeO₃ is also maintained during CO₂ electrolysis. Analysis of the gaseous products indicates that only CO is formed, and the rate of CO formation agrees well with that of a four‐electron reduction process, suggesting that the reduction of CO₂ to CO proceeds selectively. It is also confirmed that almost no coke is deposited on the Ni–Fe–LSFM cathode after CO₂ electrolysis.     

Radon fluxes in tropical forest ecosystems of Brazilian Amazonia: night-time CO2 net ecosystem exchange derived from radon and eddy covariance methods

Radon‐222 (Rn‐222) is used as a transport tracer of forest canopy–atmosphere CO₂ exchange in an old‐growth, tropical rain forest site near km 67 of the Tapajós National Forest, Pará, Brazil. Initial results, from month‐long periods at the end of the wet season (June–July) and the end of the dry season (November–December) in 2001, demonstrate the potential of new Rn measurement instruments and methods to quantify mass transport processes between forest canopies and the atmosphere. Gas exchange rates yield mean canopy air residence times ranging from minutes during turbulent daytime hours to greater than 12 h during calm nights. Rn is an effective tracer for net ecosystem exchange of CO₂ (CO₂ NEE) during calm, night‐time hours when eddy covariance‐based NEE measurements are less certain because of low atmospheric turbulence. Rn‐derived night‐time CO₂ NEE (9.00±0.99 μmol m^?2 s^?1 in the wet season, 6.39±0.59 in the dry season) was significantly higher than raw uncorrected, eddy covariance‐derived CO₂ NEE (5.96±0.51 wet season, 5.57±0.53 dry season), but agrees with corrected eddy covariance results (8.65±1.07 wet season, 6.56±0.73 dry season) derived by filtering out lower NEE values obtained during calm periods using independent meteorological criteria. The Rn CO₂ results suggest that uncorrected eddy covariance values underestimate night‐time CO₂ loss at this site. If generalizable to other sites, these observations indicate that previous reports of strong net CO₂ uptake in Amazonian terra firme forest may be overestimated.     

Scattering Efficiency and LSPR Tunability of Bimetallic Ag,Au, and Cu Nanoparticles

Scattering efficiencies of Ag–Cu, Ag–Au, and Au–Cu alloy nanoparticles are studied based on Mie theory for their possible applications in solar cells. The effect of size (radius), surrounding medium, and alloy composition on the scattering efficiency at the localized surface plasmon resonance (LSPR) wavelengths has been reported. In the alloy nanoparticles of Ag_1?x Cu _x , Au_1?x Cu _x and Ag_1?x Au _x ; the scattering efficiency gets red-shifted with increase in x. Moreover, the scattering efficiency enhancement can be tuned and controlled with both the alloy composition and the surrounding medium refractive index. A linear relationship which is in good agreement to the experimental observations between the scattering efficiency and metal composition in the alloys are found. The effect of nanoparticle size and LSPR wavelength (scattering peak position) on the full width half maxima and scattering efficiency has also been studied. Comparison of Au–Ag, Au–Cu, and Ag–Cu alloy nanoparticles with 50-nm radii shows the optical response of Ag–Cu alloy nanoparticle with wide bandwidth in the visible region of the electromagnetic spectrum making them suitable for plasmonic solar cells. Further, the comparison of Ag–Cu alloy and core@shell nanoparticles of similar size and surrounding medium shows that Cu@Ag nanoparticle exhibits high scattering efficiency with nearly the same bandwidth.     

Influence of carbon dioxide enrichment, ozone and nitrogen fertilization on cotton (Gossypium hirsutum L.) leaf and root composition

The objective of this study was to test whether elevated [CO₂], [O₃] and nitrogen (N) fertility altered leaf mass per area (LMPA), non‐structural carbohydrate (TNC), N, lignin (LTGA) and proanthocyanidin (PA) concentrations in cotton (Gossypium hirsutum L.) leaves and roots. Cotton was grown in 14 dm³ pots with either sufficient (0·8 g N dm ^{? 3}) or deficient (0·4 and 0·2 g N dm ^{? 3}) N fertilization, and treated in open‐top chambers with either ambient or elevated ( + 175 and + 350 μ mol mol ^{? 1}) [CO₂] in combination with either charcoal‐filtered air (CF) or non‐filtered air plus 1·5 times ambient [O₃]. At about 50 d after planting, LMPA, starch and PA concentrations in canopy leaves were as much as 51–72% higher in plants treated with elevated [CO₂] compared with plants treated with ambient [CO₂], whereas leaf N concentration was 29% lower in elevated [CO₂]‐treated plants compared with controls. None of the treatments had a major effect on LTGA concentrations on a TNC‐free mass basis. LMPA and starch levels were up to 48% lower in plants treated with elevated [O₃] and ambient [CO₂] compared with CF controls, although the elevated [O₃] effect was diminished when plants were treated concurrently with elevated [CO₂]. On a total mass basis, leaf N and PA concentrations were higher in samples treated with elevated [O₃] in ambient [CO₂], but the difference was much reduced by elevated [CO₂]. On a TNC‐free basis, however, elevated [O₃] had little effect on tissue N and PA concentrations. Fertilization treatments resulted in higher PA and lower N concentrations in tissues from the deficient N fertility treatments. The experiment showed that suppression by elevated [O₃] of LMPA and starch was largely prevented by elevated [CO₂], and that interpretation of [CO₂] and [O₃] effects should include comparisons on a TNC‐free basis. Overall, the experiment indicated that allocation to starch and PA may be related to how environmental factors affect source–sink relationships in plants, although the effects of elevated [O₃] on secondary metabolites differed in this respect.     

Mo‐Based Ultrasmall Nanoparticles on Hierarchical Carbon Nanosheets for Superior Lithium Ion Storage and Hydrogen Generation Catalysis

Constructing 3D hierarchical architecture consisting of 2D hybrid nanosheets is very critical to achieve uppermost and stable electrochemical performance for both lithium‐ion batteries (LIBs) and hydrogen evolution reaction (HER). Herein, a simple synthesis of uniform 3D microspheres assembled from carbon nanosheets with the incorporated MoO₂ nanoclusters is demonstrated. The MoO₂ nanoclusters can be readily converted into the molybdenum carbide (Mo₂C) nanocrystals by using high temperature treatment. Such assembling architecture is highly particular for preventing Mo‐based ultrasmall nanoparticles from coalescing or oxidizing and endowing them with rapid electron transfer. Consequently, the MoO₂/C hybrids as LIB anode materials deliver a specific capacity of 625 mA h g^?1 at 1600 mA g^?1 even after 1000 cycles, which is among the best reported values for MoO₂‐based electrode materials. Moreover, the Mo₂C/C hybrids also exhibit excellent electrocatalytic activity for HER with small overpotential and robust durability in both acid and alkaline media. The present work highlights the importance of designing 3D structure and controlling ultrasmall Mo‐based nanoparticles for enhancing electrochemical energy conversion and storage applications.     

Infection with the parasitic angiosperm Striga hermonthica influences the response of the C3 cereal Oryza sativa to elevated CO2

Upland rice (Oryza sativa L.) was grown at both ambient (350 μmol mol^?1) and elevated (700 μmol mol^?1) CO₂ in either the presence or absence of the root hemi‐parasitic angiosperm Striga hermonthica (Del) Benth. Elevated CO₂ alleviated the impact of the parasite on host growth: biomass of infected rice grown at ambient CO₂ was 35% that of uninfected, control plants, while at elevated CO₂, biomass of infected plants was 73% that of controls. This amelioration occurred despite the fact that O. sativa grown at elevated CO₂ supported both greater numbers and a higher biomass of parasites per host than plants grown at ambient CO₂. The impact of infection on host leaf area, leaf mass, root mass and reproductive tissue mass was significantly lower in plants grown at elevated as compared with ambient CO₂. There were significant CO₂ and Striga effects on photosynthetic metabolism and instantaneous water‐use efficiency of O. sativa. The response of photosynthesis to internal [CO₂] (A/C_i curves) indicated that, at 45 days after sowing (DAS), prior to emergence of the parasites, uninfected plants grown at elevated CO₂ had significantly lower CO₂ saturated rates of photosynthesis, carboxylation efficiencies and ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) contents than uninfected, ambient CO₂‐grown O. sativa. In contrast, infection with S. hermonthica prevented down‐regulation of photosynthesis in O. sativa grown at elevated CO₂, but had no impact on photosynthesis of hosts grown at ambient CO₂. At 76 DAS (after parasites had emerged), however, infected plants grown at both elevated and ambient CO₂ had lower carboxylation efficiencies and Rubisco contents than uninfected O. sativa grown at ambient CO₂. The reductions in carboxylation efficiency (and Rubisco content) were accompanied by similar reductions in nitrogen concentration of O. sativa leaves, both before and after parasite emergence. There were no significant CO₂ or infection effects on the concentrations of soluble sugars in leaves of O. sativa, but starch concentration was significantly lower in infected plants at both CO₂ concentrations. These results demonstrate that elevated CO₂ concentrations can alleviate the impact of infection with Striga on the growth of C₃ hosts such as rice and also that infection can delay the onset of photosynthetic down‐regulation in rice grown at elevated CO₂.     

An efficient method for the synthesis of phenacyl ester‐protected dipeptides using neutral alumina‐supported sodium carbonate ‘Na2CO3/n‐Al2O3’

In the synthesis of dipeptides (Boc‐AA¹‐AA²‐OPac: AA¹ and AA² represent amino acids) protected by phenacyl (Pac) ester, amines and solid bases as the base for the conversion of the trifluoroacetic acid (TFA) salt of the amino component (TFA·H‐AA²‐OPac) into the corresponding free amino component (H‐AA²‐OPac) were examined. The synthesis of a dipeptide (Boc‐Ala‐Gly‐OPac) using amines for the conversion afforded an unsatisfactory yield with by‐products. On the other hand, the use of neutral alumina‐supported Na₂CO₃ (Na₂CO₃/n‐Al₂O₃) as a solid base for the conversion provided the dipeptide in a quantitative yield without by‐products. The application of Na₂CO₃/n‐Al₂O₃ to the synthesis of some dipeptides protected by Pac ester gave the desired peptides in excellent yields. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

A Porphyrin/Graphene Framework: A Highly Efficient and Robust Electrocatalyst for Carbon Dioxide Reduction

Developing immobilized molecular complexes, which demonstrate high product efficiencies at low overpotential in the electrochemical reduction of CO₂ in aqueous media, is essential for the practical production of reduction products. In this work, a simple and facile self‐assembly method is demonstrated by electrostatic interaction and π–π stacking for the fabrication of a porphyrin/graphene framework (FePGF) composed of Fe(III) tetraphenyltrimethylammonium porphyrin and reduced liquid crystalline graphene oxide that can be utilized for the electrocatalytic reduction of CO₂ to CO on a glassy carbon electrode in aqueous electrolyte. The FePGF results in an outstanding robust catalytic performance for the production of CO with 97.0% faradaic efficiency at an overpotential of 480 mV and superior long‐term stability relative to other heterogeneous molecular complexes of over 24 h (cathodic energy efficiency: 58.1%). In addition, a high surface area carbon fiber paper is used as a substrate for FePGF catalyst, resulting in enhanced current density of 1.68 mA cm^?2 with 98.7% CO faradaic efficiency at an overpotential of 430 mV for 10 h, corresponding to a turnover frequency of 2.9 s^?1 and 104 400 turnover number. Furthermore, FePGF/CFP has one of the highest cathodic energy efficiencies (60.9%) reported for immobilized metal complex catalysts.     

Realizing Interfacial Electronic Interaction within ZnS Quantum Dots/N‐rGO Heterostructures for Efficient Li–CO2 Batteries

With high theoretical energy density, rechargeable metal–gas batteries (e.g., Li–CO₂ battery) are considered as one of the most promising energy storage devices. However, their practical applications are hindered by the sluggish reaction kinetics and discharge product accumulation during battery cycling. Currently, the solutions focus on exploration of new catalysts while the thorough understanding of their underlying mechanisms is often ignored. Herein, the interfacial electronic interaction within rationally designed catalysts, ZnS quantum dots/nitrogen‐doped reduced graphene oxide (ZnS QDs/N‐rGO) heterostructures, and their effects on transformation and deposition of discharge products in the Li–CO₂ battery are revealed. In this work, the interfacial interaction can both enhance the catalytic activities of ZnS QDs/N‐rGO heterostructures and induce the nucleation of discharge products to form a homogeneous Li₂CO₃/C film with excellent electronic transmission and high electrochemical activities. When the batteries cycle within a cutoff specific capacity of 1000 mAh g^?1 at a current density of 400 mA g^?1, the cycling performance of the Li–CO₂ battery using a ZnS QDs/N‐rGO cathode is over 3 and 9 times than those coupled with a ZnS nanosheets (NST)/N‐rGO cathode and a N‐rGO cathode, respectively. This work provides comprehensive understandings on designing catalysts for Li–CO₂ batteries as well as other rechargeable metal–gas batteries.     

A sensitive SERS quantitative analysis method for Ni2+ by the dimethylglyoxime reaction regulating a graphene oxide nanoribbon catalytic gold nanoreaction

The nanogold reaction between HAuCl₄ and trisodium citrate (TCA) proceeded very slowly at 60°C in a water bath. The as‐prepared graphene oxide nanoribbons (GONRs) exhibited strong catalysis during the reaction to form gold nanoparticles (Au NPs) and appeared as a strong surface‐enhanced Raman scattering (SERS) peak at 1616 cm^?1 in the presence of the molecular probe Victoria blue 4R (VB4r). With increase in GONR concentration, the SERS peak increased due to increased formation of Au NPs. Upon addition of dimethylglyoxime (DMG) ligand, which was adsorbed onto the GONR surface to inhibit GONR catalysis, the SERS peak decreased. When Ni²⁺ was added, a coordination reaction between DMG and Ni²⁺ took place to form stable complexes of [Ni (DMG)₂]²⁺ and the release of free GONR catalyst that resulted in the SERS peak increasing linearly. A SERS quantitative analysis method for Ni²⁺ was therefore established, with a linear range of 0.07–2.8 μM, and a detection limit of 0.036 μM Ni²⁺.     

Ozone and density affect the response of biomass and seed yield to elevated CO2 in rice

Tropospheric O₃ reduces growth and yield of many crop species, whereas CO₂ ameliorates the negative effects of O₃. Thus, in a combined elevated CO₂ and O₃ atmosphere, seed yield is at least restored to that of charcoal‐filtered (CF) air at ambient CO₂. The CO₂‐induced yield increase in CF air is highly variable, suggesting other potential resource limitations. To understand such variability in response, we tested that (1) competition for resources precludes some of the CO₂ enhancement on biomass and yield; and (2) O₃ reduces competition in elevated CO₂. We grew rice (Oryza sativa L.) at five densities in CF and O₃‐fumigated (+O3) air at ambient (A) and elevated [CO₂] (+CO2) in 1997 and 1998. O₃ reduced biomass by 25% and seed yield by 13–20% in A, but had little effect in +CO2. A competition model of biomass and yield response to density based on resource availability without competition showed that fewer resources were used for biomass in +O3 than in CF (average 53% vs. 70%) in A, while in +CO2 85% of resources were used for biomass regardless of O₃ suggesting greater depletion of resources. The enhanced biomass response to CO₂ with O₃ is consistent with a 22% greater CO₂ enhancement ratio [mass in +CO2 air/mass in A air; enhancement ratio (ER)] in +O3 than in CF air. For seed yield, few resources were used (average 17% and 25% for CF in 1997 and 1998, respectively), and ER was 13% greater in +O3. With competition the rate of change of individual plant biomass to density was not affected by +CO2 in CF air in 1997 but was increased 19% with more nutrients in 1998, indicating resource limitations with +CO2. The rate of change of individual plant yield to density was reduced with CO₂ in 1997 and unchanged in 1998 showing a different response to resource limitation for reproductive biomass. The resource use in +O3‐A suggested that increased density and soil fertility might compensate for pollutant damage. Although ambient [O₃] can modulate the response to elevated CO₂, resource limitation precludes the CO₂ fertilization impact and both factors need consideration for better management and forecasts of future productivity.