Self-Catalyzed Rechargeable Lithium-Air Battery by in situ Metal Ion Doping of Discharge Products: A Combined Theoretical and Experimental Study

Lithium-air battery has emerged as a viable electrochemical energy technology;yet a substantial overpotential is typically observed,due to the insulating nature of the discharge product Li_(2)O_(2) that hinders the reaction kinetics and device performance.Furthermore,finite solid–solid/-liquid interfaces are formed between Li_(2)O_(2) and catalysts and limit the activity of the electrocatalysts in battery reactions,leading to inadequate electrolytic efficiency.Herein,in-situ doping of Li_(2)O_(2) by select metal ions is found to significantly enhance the lithium-air battery performance,and Co^(2+)stands out as the most effective dopant among the series.This is ascribed to the unique catalytic activity of the resulting Co-O_(x) sites towards oxygen electrocatalysis,rendering the lithium-air battery self-catalytically active.Theoretical studies based on density functional theory calculations show that structural compression occurs upon Co^(2+)doping,which lowers the energy barrier of Li_(2)O_(2) decomposition.Results from this study highlight the significance of in situ electrochemical doping of the discharge product in enhancing the performance of lithium-air battery.

Electrocatalysts based on metal@carbon core@shell nanocomposites:An overview

Developing low-cost, high-performance catalysts is of fundamental significance for electrochemical energy conversion and storage. In recent years, metal@carbon core@shell nanocomposites have emerged as a unique class of functional nanomaterials that show apparent electrocatalytic activity towards a range of reactions, such as hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and CO2 reduction reaction, that are important in water splitting, fuel cells and metal-air batteries. The activity is primarily attributed to interfacial charge transfer from the metal core to the carbon shell that manipulate the electronic interactions between the catalyst surface and reaction intermediates, and varies with the structures and morphologies of the metal core(elemental composition, core size, etc.) and carbon shell(doping,layer thickness, etc.). Further manipulation can be achieved by the incorporation of a third structural component. A perspective is also included highlighting the current gap between theoretical modeling and experimental results, and technical challenges for future research.

Electrocatalytic generation of reactive species and implications in microbial inactivation

Controlling microbial proliferation in water systems,including wastewater,recreational water,and drinking water,is essential to societal health.Microbial inactivation through electrochemically generated reactive species(RS)mediated pathways provides an effective route toward this microbial control.Herein we provide an overview of recent progress toward electrocatalytic generation of RS and their application in water disinfection,with a focus on the selective production of RS,the microorganism interactions with RS(including both RS mechanisms of action and innate microorganism responses to RS),and practical implementation of electrochemically generated RS for microbial inactivation.The article is concluded with a perspective where the challenges and opportunities of RS‐based electrochemical disinfection of water are highlighted,along with possible future research directions.

Intraparticle Charge Delocalization through Conjugated Metal-Ligand Interfacial Bonds:Effects of Metal d Electrons

Intraparticle charge delocalization occurs when metal nanoparticles are functionalized with organic capping ligands through conjugated rnetal-ligand interfacial bonds. In this study, metal nanoparticles of 5d metals （Ir, Pt, and Au） and 4d metals （Ru, Rh, and Pd） were prepared and capped with ethynylphenylacetylene and the impacts of the number of metal d electrons on the nanoparticle optoelectronic properties were examined. Both FTIR and photoluminescence measurements indicate that intraparticle charge delocalization was en- hanced with the increase of the number of d electrons in the same period with palladium being an exception.

Siliceous mesocellular foam supported Cu catalysts for promoting non-thermal plasma activated CO_(2) hydrogenation toward methanol synthesis

Electrified non-thermal plasma (NTP) catalytic hydrogenation is the promising alternative to the thermal counterparts, being able to be operated under mild conditions and compatible with green electricity/hydrogen. Rational design of the catalysts for such NTP-catalytic systems is one of the keys to improve the process efficiency. Here, we present the development of siliceous mesocellular foam (MCF) supported Cu catalysts for NTP-catalytic CO_(2) hydrogenation to methanol. The findings show that the pristine MCF support with high specific surface area and large mesopore of 784 m2·g−1 and ~8.5 nm could promote the plasma discharging and the diffusion of species through its framework, outperforming other control porous materials (viz., silicalite-1, SiO_(2), and SBA-15). Compared to the NTP system employing the bare MCF, the inclusion of Cu and Zn in MCF (i.e., Cu1Zn1/MCF) promoted the methanol formation of the NTP-catalytic system with a higher space-time yield of methanol at ~275 μmol·g_(cat)^(−1)·h^(−1) and a lower energy consumption of 26.4 kJ^(−1)·mmol_(CH_(3)OH)^(-1) (conversely, ~225 μmol·g_(cat)^(−1)·h^(−1) and ~71 kJ^(−1)·mmol_(CH_(3)OH)^(-1), respectively, for the bare MCF system at 10.1 kV). The findings suggest that inclusion of active metal sites (especially Zn species) could stabilize the CO_(2)/CO-related intermediates to facilitate the surface reaction toward methanol formation.

Formation of hierarchically 3D cactus-like architecture as efficient Mott-Schottky electrocatalyst for long-life Li-S batteries

Searching for new promising electrocatalysts with favorable architectures allowing abundant active sites and remarkable structure stability is an urgent task for the practical application of lithium-sulfur(Li-S)batteries.Herein,inspired by the structure of natural cactus,a new efficient and robust electrocatalyst with three-dimensional(3D)hierarchical cactus-like architecture constructed by functional zero-dimensional(0D),one-dimensional(1D),and two-dimensional(2D)components is developed.The cactus-inspired catalyst(denoted as Co@NCNT/NCNS)consists of N-doped carbon nanosheets(NCNS)and standing Ndoped carbon nanotubes(NCNT)forest with embedded Co nanoparticles on the top of NCNT,which was achieved by an in situ catalytic growth technique.The unique structure design integrates the advantages of 0D Co accelerating catalytic redox reactions,1D NCNT providing a fast electron pathway,and 2D NCNS assuring strong structure stability.Especially,the rich Mott-Schottky heterointerfaces between metallic Co and semiconductive NCNT can further facilitate the electron transfer,thus improving the electrocatalyst activity.Consequently,a Li-S battery with the Co@NCNT/NCNS modified separator achieves ultralong cycle life over 4000 cycles at 2 C with ultralow capacity decay of 0.016%per cycle,much superior over that of recently reported batteries.This work provides a new strategy for developing ultra-stable catalysts towards long-life Li-S batteries.

Nutritional Composition and Assessment of Gracilaria lemaneiformis Bory

The chemical composition, mineral elements, vitamins, free fatty acids and amino acid content of the edible red alga Gracilaria lemaneiformis Bory, grown in the sea near Nan＇ao island, Guangdong Province, were analyzed in the present study. Gracilaria lemaneiformis Bory showed a total sugar content of 14.65%. The protein content was 21%, of which approximately 41% was determined to be essential amino acids （EAA）. The major amino acid components were glutamic acid, leucine, arginine, and alanine. Of the EAA assayed, methionine and cysteine appeared to be the most limiting amino acids compared with the EAA pattern provided by Food and Agricultural Organization of the United Nations. The total lipids content was 0.87% and comprised a high composition of unsaturated fatty acids （61%）, mainly as linoleic acid and oleic acid, and a little amount of polyunsaturated fatty acid; palmitic acid was the main component （39%） of saturated acids. Relatively high levels of vitamin C, iodine, phosphorus, and zinc were also present in G. lemaneiformis. The nutritional composition between G. lemaneiformis and Nostoc flagelliforme, a rare alga that is widely eaten in Chinese society, was compared. The results suggest that N. flagelliforme can be substituted for by G. lemaneiformis, not only because of their similar shape, but also because of their approximate nutritional composition. Gracilaria lemaneiformis may possibly serve as a potential healthy food in human diets in the future.

Enhanced electrocatalytic activity of Co@N-doped carbon nanotubes by ultrasmall defect-rich TiO2 nanoparticles for hydrogen evolution reaction

Despite being technically possible, splitting water to generate hydrogen is practically unfeasible, mainly because of the lack of sustainable and efficient earth-abundant catalysts for the hydrogen-evolution reaction （HER）. Herein, we report a durable and highly active electrochemical HER catalyst based on defect-rich TiO2 nanoparticles loaded on Co nanoparticles@N-doped carbon nanotubes （D-TiOdCo@NCT） synthesized by electrostatic spinning and a subsequent calcining process. The ultrasmall TiO2 nanoparticles are 1.5-2 nm in size and have a defect-rich structure of oxygen vacancies. D-TiO2/Co@NCT exhibits excellent HER catalytic activity in an acidic electrolyte （0.5 M H2SO4）, with a low onset potential of -57.5 mV （1 mA·cm^-2）, a small Tafel slope of 73.5 mV·dec^-1, and extraordinary long-term durability. X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, and theoretical calculations confirm that the Ti3. defect-rich structure can effectively regulate the catalytic activity for electrochemical water splitting.

A synchronous nucleation and passivation strategy for controllable synthesis of Au36(PA)24: unveiling the formation process and the role of Au22(PA)18 intermediate

Despite the recent progress on controllable synthesis of alkynyl-protected Au nanoclusters,the effective synthetic means are very limited and the cluster formation process still remains puzzling.Here,we develop a novel synchronous nucleation and passivation strategy to fabricate Au36(PA)24(PA=phenylacetylenyl) nanoclusters with high yield.In Au36(PA)24formation process,Au22(PA)18as key intermediate was identified.Meanwhile,Au22(PA)18can be synthesized under a low amount of reductant,and by employing more reductants,Au22(PA)18can turn into Au36(PA)24eventually.Moreover,the structure evolution from Au22(PA)18to Au36(PA)24is proposed,where four Au13cuboctahedra can yield one Au28kernel.Finally,the ratiocination is verified by the good accordance between the predicted intermediate/product ratio and the experimental value.This study not only offers a novel synthetic strategy,but also sheds light on understanding the structural evolution process of alkynyl-protected Au nanoclusters at atomic level.

Short-term effects of excessive anaerobic reaction time on anaerobic metabolism of denitrifying polyphosphate- accumulating organisms linked to phosphorus removal and N20 production

The short-term effect of anaerobic reaction time （AnRT） （i.e., 90, 120 and 150 min） on the denitrifying phosphorus （P） removal performance and N20 production was examined using a denitrifying enhanced biologic phosphorus removal （EBPR） sludge acclimatized with mixed acetate （HAc） and propionate （Pro） （in the molar ratio 3 ： 1） as carbon sources. The results showed that when the AnRT was prolonged from 90 to 150 rain, the anaerobic polyhydroxyalkanoate （PHA） synthesis was decreased by 15.3%. Moreover, the ineffective PHA consumption occurred in anaerobic phases and contributed to an increased NO2-N accumulation and higher flee nitrous acid （FNA） concentrations （〉t0.001-0.0011 mg HNO2-N/L） in the subsequent anoxic phases, causing a severe inhibition on anoxic P-uptake and denitrification. Accordingly, the total nitrogen （TN） and total phosphorus （TP） removal efficiencies dropped by approximately 6.3% and 85.5%, respectively; and the ratio of anoxic NzO-N production to TN removal increased by approximately 3.8%. The fluorescence in situ hybridization （FISH） analysis revealed that the sludge was mainly dominated by Accumulibacter （62.0% （SEmean = 1.5%））. In conclu- sion, the short-term excessive anaerobic reaction time negatively impacted denitrifying P removal performance and stimulated more NzQ production, and its effect on P removal was more obvious than that on nitrogen removal.

Silver nanocubes monolayers as a SERS substrate for quantitative analysis

Surface-enhanced Raman scattering(SERS)is a powerful spectroscopic tool in quantitative analysis of molecules,where the substrate plays a critical role in determining the detection performance.Herein,a silver nanocubes/polyelectrolyte/gold film sandwich structure was prepared as a reproducible,highperformance SERS substrate by the wate r/oil inte rfacial assembly method.In addition to the hot spots on the nanocubes surface,the edge-to-edge interspace of the Ag nanocubes led to marked enhancement of the SERS intensity,with a limit of detection of 10~(11)mol/L and limit of quantitation of 10~(10)mol/L for crystal violet.When rhodamine 6 G and crystal violet were co-adsorbed on the Ag nanocube surfaces,the characteristic SERS peaks of the two molecules remained well resolved and separated,and the peak intensities varied with the respective concentration,which could be exploited for concurrent detection of dual molecules.Results from this work indicate that organized ensembles of Ag nanocubes can serve as effective SERS substrate can for sensitive analysis for complex molecular systems.

Two-dimensional porous zinc cobalt sulfide nanosheet arrays with superior electrochemical performance for supercapatteries

Unique two-dimensional(2D)porous nanosheets with overwhelmingly rich channels and large specific surface area exhibit superior electrochemical capacitance performance,as compared to the conventional zero-and one-dimensional counterparts.As ternary transition metal sulfides(TMSs)are well recognized for their high electrochemical activity and capacity,and the replacement of oxygen with sulfur may result in high stability and flexible properties of the nanomaterials,as compared to transition metal oxides,herein we report the synthesis of 2D porous nanosheet arrays of Zn_(x)Co_(1-x)S(x=0,0.25,0.5,0.75,and 1)via a facile hydrothermal process.Due to the synergistic effect of the metal components and a unique 2D porous structure,the Zn_(0.5)Co_(0.5)S electrode was found to stand out as the best among the series,with a high specific capacity of 614 C g^(-1)at 1 A g^(-1)and excellent cycle retention rate of 90%over 10,000 cycles at 10 A g^(-1).Notably,a supercapattery based on a Zn_(0.5)Co_(0.5)S positive electrode and an activated carbon(AC)negative electrode(Zn_(0.5)Co_(0.5)S//AC)was found to display a 1.6 V voltage window,a 61 mA h g^(-1)specific capacity at 1 A g^(-1),a 49 Wh kg^(-1)energy density at 957 W kg^(-1)power density,and excellent cycling performance(88%over 10,000 cycles),suggesting tremendous potential of Zn_(0.5)Co_(0.5)S in the development of high-performance supercapattery devices.

Rapid preparation of carbon-supported ruthenium nanoparticles by magnetic induction heating for efficient hydrogen evolution reaction in both acidic and alkalinemedia

Ruthenium has been hailed as a competitive alternative for platinum toward hydrogen evolution reaction(HER),a critical process in electrochemical water splitting.In this study,we successfully prepare metallic Ru nanoparticles supported on carbon paper by utilizing a novel magnetic induction heating(MIH)method.The samples are obtained within seconds,featuring a Cl-enriched surface that is unattainable via conventional thermal annealing.The best sample within the series shows a remarkable HER activity in both acidic and alkaline media with an overpotential of only-23 and-12 mV to reach the current density of 10 mA/cm^(2),highly comparable to that of the Pt/C benchmark.Theoretical studies based on density functional theory show that the excellent electrocatalytic activity is accounted by the surface metal-Cl species that facilitate charge transfer and downshift the d-band center.Results from this study highlight the unique advantages of MIH in rapid sample preparation,where residual anion ligands play a critical role in manipulating the electronic properties of the metal surfaces and the eventual electrocatalytic activity.

Oxygen Reduction Reaction Catalyzed by Carbon-Supported Platinum Few-Atom Clusters:Significant Enhancement by Doping of Atomic Cobalt

Oxygen reduction reaction(ORR)plays an important role in dictating the performance of various electrochemical energy technologies.As platinum nanoparticles have served as the catalysts of choice towards ORR,minimizing the cost of the catalysts by diminishing the platinum nanoparticle size has become a critical route to advancing the technological development.Herein,first-principle calculations show that carbon-supported Pt9 clusters represent the threshold domain size,and the ORR activity can be significantly improved by doping of adjacent cobalt atoms.This is confirmed experimentally,where platinum and cobalt are dispersed in nitrogen-doped carbon nanowires in varied forms,single atoms,few-atom clusters,and nanoparticles,depending on the initial feeds.The sample consisting primarily of Pt_(2~7)clusters doped with atomic Co species exhibits the best mass activity among the series,with a current density of 4:16Amg^(-1)_(Pt)at+0.85V vs.RHE that is almost 50 times higher than that of commercial Pt/C.

Nanowrinkled Carbon Aerogels Embedded with FeN_(x) Sites as Effective Oxygen Electrodes for Rechargeable Zinc-Air Battery

Rational design of single-metal atom sites in carbon substrates by a flexible strategy is highly desired for the preparation of high-performance catalysts for metal-air batteries.In this study,biomass hydrogel reactors are utilized as structural templates to prepare carbon aerogels embedded with single iron atoms by controlled pyrolysis.The tortuous and interlaced hydrogel chains lead to the formation of abundant nanowrinkles in the porous carbon aerogels,and single iron atoms are dispersed and stabilized within the defective carbon skeletons.X-ray absorption spectroscopy measurements indicate that the iron centers are mostly involved in the coordination structure of FeN_(4),with a minor fraction(ca.1/5)in the form of FeN_(3)C.First-principles calculations show that the FeN_(x) sites in the Stone-Wales configurations induced by the nanowrinkles of the hierarchically porous carbon aerogels show a much lower free energy than the normal counterparts.The resulting iron and nitrogen-codoped carbon aerogels exhibit excellent and reversible oxygen electrocatalytic activity,and can be used as bifunctional cathode catalysts in rechargeable Zn-air batteries,with a performance even better than that based on commercial Pt/C and RuO_(2) catalysts.Results from this study highlight the significance of structural distortions of the metal sites in carbon matrices in the design and engineering of highly active single-atom catalysts.

Ultrafast Preparation of Nonequilibrium FeNi Spinels by Magnetic Induction Heating for Unprecedented Oxygen Evolution Electrocatalysis

Carbon-supported nanocomposites are attracting particular attention as high-performance,low-cost electrocatalysts for electrochemical water splitting.These are mostly prepared by pyrolysis and hydrothermal procedures that are time-consuming(from hours to days)and typically difficult to produce a nonequilibrium phase.Herein,for the first time ever,we exploit magnetic induction heating-quenching for ultrafast production of carbon-FeNi spinel oxide nanocomposites(within seconds),which exhibit an unprecedentedly high performance towards oxygen evolution reaction(OER),with an ultralow overpotential of only+260 mV to reach the high current density of 100 mA cm^(-2).Experimental and theoretical studies show that the rapid heating and quenching process(ca.10^(3)K s^(-1))impedes the Ni and Fe phase segregation and produces a Cl-rich surface,both contributing to the remarkable catalytic activity.Results from this study highlight the unique advantage of ultrafast heating/quenching in the structural engineering of functional nanocomposites to achieve high electrocatalytic performance towards important electrochemical reactions.