Search

Drug-drug cocrystals, which can regulate physicochemical properties of individual drugs and might produce synergistic therapeutic effects, have drawn growing interest in the pharmaceutical industry. In this study, a novel drug-drug (1:1) cocrystal hydrate of slightly water-soluble dihydromyricetin (DMY) and highly water-soluble pentoxifylline (PTX), DMY-PTX•H2O (1), was prepared by a slurry method. The single-crystal X-ray diffraction results reveal that the cocrystal is formed through hydrogen-bonding interactions between hydroxyl groups of DMY and four acceptors of PTX. The dynamic vapour sorption results indicate that the cocrystal displays reduced hydrophilicity compared with DMY. It is found that cocrystal formation narrows the solubility difference between two parent drugs. The equilibrium solubility of PTX decreases greatly, while that of DMY increases slightly. As a result, DMY and PTX are synchronously and sustainedly released from the cocrystal. Further, a synergistic anti-cancer effect of the cocrystal DMY-PTX•H2O (1) on HepG2 cells in vitro at a drug concentration of 100 μM was discovered. This study brings evidence of cocrystallization as a successful approach for synchronous sustained-release of two drugs with substantially different aqueous solubility.

Rechargeable multivalent-ion batteries are considered as sustainable energy storage solutions that can supplement the current lithium-ion technology. Their large-scale application is however hinder...

Black phosphorus is a potential candidate material for next-generation energy storage devices and has attracted tremendous interest because of its advantageous structural and electrochemical properties, including its large theoretical capacity, high carrier mobility, and low redox potential. However, its practical applicability has remained low owing to its difficult of preparation, large volume expansion during cycling, and poor electronic conductivity. To this end, there have been significant efforts to improve its synthesis methods and electrochemical performance. A number of black-phosphorus-based composite materials have been developed and investigated. Herein, we provide an up-to-date account of the recent progress made in research on black-phosphorus-based materials for use in rechargeable batteries and supercapacitors. We review the available synthesis methods and basic properties of black phosphorus and discuss its applicability in Li-, Na-, K-, Mg-, Al-ion and Li-S batteries as well as supercapacitors. We also summarize the existing challenges and future opportunities and offer our perspective on the possible directions for future research in this area.

Two-dimensional covalent organic frameworks (COFs) are an emerging class of semiconducting materials for photocatalysis solar fuel production. They uniquely feature compositional and structural diversities (as opposed to inorganic semiconductors) as well as high crystallinity (as opposed to other organic semiconductors), and thereby hold great potential that is just beginning to be unveiled. Here, we provide an up-to-date account of the latest advances on the design and engineering of COF-based materials for photocatalytic H2 production or CO2 reduction. The review begins with an introduction of the background and fundamentals about COF-based photocatalysis. It is then followed by discussion about recent progress on their preparation, understanding of charge dynamics and strategies for improving photocatalytic performances. A short perspective on the opportunities and further directions is presented at the end.

Water-splitting electrolysis, using a renewable power source, has been widely considered as a promising energy conservation and storage technology that is environmentally friendly. In order to lower the required energy barrier and to improve the energy-conversion efficiency of hydrogen evolution and oxygen evolution on the electrodes, highly efficient and durable electrocatalysts are essential. To date, various preparation methods and theoretical models have been developed to accelerate the catalyst design and to further understand the associated electrocatalytic mechanism. In this issue of MRS Bulletin, all aspects of non-noble metal-based electrocatalysts for water splitting involving standard methodology, surface electronic structure engineering, morphology design, interface effects, pH operation range, activity descriptors, and operational stability are discussed. These discussions indicate the importance of materials innovations for the realization of highly efficient and durable electrocatalysts for large-scale cost-effective water splitting.

Development of efficient molecular catalysts for photocatalytic CO2 reduction is desirable but challenging. At present, the majority of reported molecular catalysts consist of the transition metal centers coordinated by N-containing ligands. Inspired by the sulfur-containing active site found in carbon monoxide dehydrogenases, we here report a novel Ni-based molecular catalyst bearing 2,6-bis([(2-pyridinylmethyl)thio]methyl) pyridine) as the pentadentate ligand. The product is assessed for photocatalytic CO2 reduction in acetonitrile/water solution using Ru(bpy)3Cl2 as the photosensitizer and triethanolamine as the electron donor. Under the optimal condition, a total of ca. 25 μmol CO is produced after 7 h visible light irradiation with a large turnover number of 63 and high selectivity of 91%.

Lithium–sulfur batteries are considered a possible next-generation energy-storage solution, but their commercial viability is still in question because of several technical challenges, including th...

The inhomogeneous properties of 5052 aluminum alloy/304 stainless steel rotary friction welded joint and the growth behavior of intermetallic compound (IMC) layer were investigated. The ultimate tensile strength (UTS) of as-welded joint in 0R location with discontinuous IMC layer reached the maximum value of 203 MPa, and that in R/2 and 3R/4 locations decreased with the increase of IMC layer thickness, but that in R/4 location was the lowest due to the initiation of crack. After post-weld heat treatment at 250 °C/20 min, the thickness of IMC layer remained invariant, but the UTS of entire joint increased from 153 MPa to 161.4 MPa. In addition, the difference of UTS along the radius direction decreased, which benefited the engineering application. During post-weld heat treatment at 450 °C, the growth of IMC layer in R/4, R/2 and 3R/4 location were faster than that in 0R location. However, the growth of IMC layer deviated from parabolic law, which was attributed to (i) a large number of dislocations, grain boundaries and storage energy in the interface, (ii) the linear growth of Fe4Al13 phase, and (iii) the effect of Cr element.

The inability of current battery technologies to keep up with the performance requirements of industry is pushing forward developments in electrochemistry. Specifically, the battery’s negative electrode, the anode, presents many unique chemical, physical and engineering challenges. Lithium-based battery technologies have dominated the past decade, but concerns about the limited supply of lithium in the Earth’s crust have led researchers to look towards alternative metal-ion technologies. Various alkali metals (such as sodium and potassium) and alkali earth metals (such as magnesium and calcium) have attracted significant research interest. In this Review, we analyse these technologies in a coherent manner, addressing the problems of each type of anode, rather than those of specific types of metal-ion batteries. Covering direct metal plating and stripping, intercalation-based, alloy-based and conversion-reaction-based anode technologies, this analysis will offer the reader a comprehensive understanding of the behaviour of different metal-ion anodes and of what can be learned by transferring knowledge between these different systems. Increasing demand for energy-storage systems will inevitably stress the Earth’s lithium supply; thus, the research focus is shifting towards other alkali and alkali earth metals. This Review compares and connects strategies to enable different multivalent and monovalent metal-ion battery anodes, including metal anodes and intercalation-based, alloy-based and conversion-reaction-based anodes.

Potassium-ion batteries are regarded as the low-cost alternative to lithium-ion batteries. However, their development is hampered by the lack of suitable electrode materials. In this work, we demonstrate that MoS2 with expanded interlayers represents a promising candidate for the electrochemical storage of potassium ions. Hierarchical interlayer-expanded MoS2 assemblies supported on carbon nanotubes are prepared via a straightforward solution method. The increased interlayer spacing not only enables the better accommodation of foreign ions, but also lowers the diffusion energy barrier and improves diffusion kinetics of ions. When investigated as the anode material of potassium ion batteries, our interlayer-expanded MoS2 assemblies exhibit an excellent electrochemical performance with large capacity (up to ∼ 520 mAhg−1), good rate capability (∼ 310 mAhg−1 at 1,000 mAg−1) and impressive cycling stability, superior to most competitors.

There is an increasing awareness of the need to pursue energy solutions with a low carbon footprint. The conventional power generation process (e.g. combustion of fossil fuels) is typically accompanied by CO2 emission. It would be very appealing if we can reverse this trend and achieve simultaneous power generation and CO2 valorization. Herein, we demonstrate the first aqueous Al–CO2 batteries using nanostructured Bi2S3 as the cathode electrocatalyst for selectively converting CO2 to formate during discharge. Bi2S3 nanoplatelets are prepared via a facile solvothermal reaction. When measured in a flow cell configuration, they enable CO2 reduction to formate with an excellent activity (current density up to >400 mA cm−2) and selectivity (∼100%). Aqueous Al–CO2 batteries are assembled by pairing the Bi2S3 cathode and the Al anode. They exhibit an impressive power output as well as great formate production rate and selectivity at the cathode. Moreover, we demonstrate that it is possible to use scrap Al from used Al beverage cans for Al–CO2 batteries to further lower the production cost.

The development of high-performance electrocatalysts holds the decisive key to the electrochemical CO2 reduction toward value-added products. Formic acid or formate is a desirable reduction product, but its selective production is often challenging. Tin based-materials have attracted great attention for formate production, and yet their performances are far from satisfactory. In this study, we reported the preparation of SnO2 nanoclusters from the controlled self-polymerization of dopamine together with SnO32−, followed by the mild-temperature calcination. The final product consisted of large primary particles that were further made of small secondary SnO2 nanocrystals. When evaluated as the electrocatalyst for CO2 reduction in 0.5 M NaHCO3, our material exhibited impressive activity, selectivity and stability for the selective CO2 reduction to formate. A peak formate Faradaic efficiency of ∼73% and large partial current density of 16.3 mA/cm2 was achieved at -0.92 V versus reversible hydrogen electrode.

Li-S batteries are a promising next-generation battery technology but are confronted with a series of fundamental challenges, in particular the notorious shuttle effect of soluble polysulfide intermediates. Current research efforts are mostly focused on designing proper host materials for the entrapment and immobilization of polysulfides. Herein, we demonstrate that electrocatalysis may play an unexpected role in Li-S batteries. Nanosized tungsten carbide particles dispersed on the carbonaceous support are prepared from the pyrolysis of phosphotungstic acid-functionalized metal-organic frameworks. Both experimental measurements and theoretical calculations demonstrate that they not only have strong affinity toward polysulfide intermediates, but also significantly accelerate the reduction of low-order polysulfides that is otherwise kinetically challenged. Using these supported tungsten carbide nanoparticles as the cathode catalyst, our Li-S batteries achieve large capacity, excellent cycling stability and impressive rate capability.

© 2019 Sodium-ion batteries (SIBs) are considered as a promising candidate to lithium-ion batteries (LIBs) owing to the inexpensive and abundant sodium reserves. However, the application of anode materials for SIBs still confront rapid capacity fading and undesirable rate capability. Here we simultaneously grow ultrafine ZnSe nanoparticles on the inner walls and the outer surface of hollow carbon nanospheres (ZnSe@HCNs), giving a unique hierarchical hybrid nanostructure that can sustain a capacity of 361.9 mAh g −1 at 1 A g −1 over 1000 cycles and 266.5 mAh g −1 at 20 A g −1 . Our investigations indicate that the sodium storage mechanism of ZnSe@HCNs electrodes is a mixture of alloying and conversion reactions, where ZnSe converts to Na 2 Se and NaZn 13 through a series of intermediate compounds. Also, a full cell is constructed from our designed ZnSe@HCNs anode and Na 3 V 2 (PO 4 ) 3 cathode. It delivers a reversible discharge capacity of about 313.1 mAh g −1 after 100 cycles at 0.5 A g −1 with high Columbic efficiency over 98.2%. The outstanding sodium storage of as-prepared ZnSe@HCNs is attributed to the confinement of ZnSe structural changes both inside/outside of hollow nanospheres during the sodiation/desodiation processes. Our work offers a promising design to enable high-power-density electrodes for the various battery systems.

Transition metal phosphides are arguably the most promising non-precious metal-based materials for hydrogen evolution reaction (HER). Unfortunately, their high preparation temperature usually results in particle sintering. It is challenging to achieve the ultra-dispersion of transition metal phosphide nanoparticles on conductive supports so as to enlarge their surface areas and reinforce their physical stability. In this study, we prepare fine MoP nanoparticles uniformly dispersed on hierarchical carbonaceous scaffolds by using strongly interacting Mo, P and C precursors. The resultant hybrid product possesses a three-dimensional open structure that allows a large fraction of MoP nanoparticles electrochemically accessible and suppresses their possible agglomeration during extended electrocatalysis. Electrochemical measurements show that the product has an impressive HER activity, only requiring an overpotential of 120 and 170 mV to achieve 10 mA/cm2 in 0.5 M H2SO4 and 1M KOH, respectively, as well as great cycling stability. Its performance can be further promoted via the controlled sulfur doping at surface to form molybdenum phosphosulfide, which reduces the overpotential at j = 10 mA/cm2 to 92 mV and 158 mV for acidic and alkaline HER.

Transition metal sulfides (TMSs) have a wide range of applications owing to their intriguing properties. Significant efforts have been devoted to nanostructuring TMSs to enhance their properties and performance, still there is a high need in general synthesis of TMS nanostructures. Herein, for the first time, a simple solvent free reactive nanocasting approach that integrates solid precursor loading, in-situ sulfuration and carbonization into a single heating step is developed for the universal synthesis of ordered mesoporous TMS@N-doped carbon composites (denoted as OM-TMS@NCs) with methionine (Met) and metal chlorides as the precursors and the mesoporous silica (SBA-15) as the hard template. A series of OM-TMS@NCs with a hexagonal mesostructure, ultra-high surface areas (430–754 m2·g−1), large pore volumes (0.85–1.32 cm3·g−1), and unique TMS stoichiometries, including MoS2, Fe7S8, Co9S8, NiS, Cu7S4 and ZnS, are obtained. Two distinct structure configurations, namely, highly dispersed ultrathin TMS nanosheets within NCs and TMS@NC co-nanowire arrays, can be obtained depending on different metals. The structure evolution of the OM-TMS@NCs over the solvent-free nanocasting process is studied in detail for a deep understanding of the synthesis. As demonstrations, these materials are promising for electrocatalytic hydrogen evolution reaction and lithium ion storage with high performances.

Modulating the charge distribution over the carbon skeleton via heteroatom doping is critical for creating active centres for efficient metal-free electrocatalysts. However, effective approaches to precisely control heteroatom co-doping to guide catalytic activities are still lacking. Herein, a P and N-coordinated fullerene-like carbon (N,P-FC) multi-functional catalyst was constructed via a facile soft-template pyrolysis method, which achieves impressive activity for the electrochemical reduction of CO2 to CO (CO2RR, 83.3% faradaic efficiency for CO (FECO), a high current density of ∼24 mA cm−2 at −0.8 V), along with high selectivity and long-term stability. The activity of N,P-FC for CO2RR is strongly dependent on the P/N atomic ratio. Also, N,P-FC possesses an impressive oxygen reduction reaction (ORR) performance with a half-wave overpotential (E1/2) of 0.910 V, 79 mV higher than that of commercial Pt/C, and it outperforms all documented carbon-based electrocatalysts. Combined theoretical calculation studies suggest that the P-coordinated C site is more active for CO2RR, while the N-coordinated neighboring C site is responsible for ORR in this catalyst. This work highlights a new concept for modulating surface charge redistribution by heteroatom co-doping and morphology control toward designing efficient and low-cost electrocatalysts.

Electrocatalytic CO2 reduction to formic acid or formate is desirable but challenging due to the lack of effective and selective electrocatalysts. Among the potential candidates, Sn-based materials have attracted wide attention, but most of them, unfortunately, do not achieve high formate selectivity until at very large overpotentials. Herein, we report the self-templated synthesis of mesoporous SnO2 nanosheets as the high-performance electrocatalyst for CO2 reduction. The final product features large surface area, abundant mesoporosity and three-dimensional hierarchical order, which are beneficial for electrochemical applications. When evaluated as the CO2 reduction electrocatalyst, mesoporous SnO2 nanosheets exhibit small onset potential, large cathodic current density, high faradaic efficiency and great stability for formate production. It is most impressive that a high formate faradaic efficiency of 83% is achieved at η ∼ 710 mV, about 150–300 mV less than that discussed in previous literature results. Moreover, we integrate mesoporous SnO2 with a dimensionally stable anode, and achieve battery-driven CO2/H2O splitting to formate/O2 with decent conversion efficiency.

Ni-Based materials are promising candidates for the electrocatalytic hydrogen oxidation reaction and hydrogen evolution reaction in alkaline solution. However, pure Ni binds hydrogen very strongly. To promote its electrocatalytic activity would require the weakening of its hydrogen binding energy. Here, we demonstrate that interstitial nitrogen doping in Ni3N can greatly promote its electrocatalytic activity. Ni3N nanoparticles are prepared from the controlled nitridation of Ni-based coordination polymer nanosheets. The resultant product exhibits excellent mass activity superior to most existing non-precious-metal-based materials and great CO-tolerance for the hydrogen oxidation reaction, as well as remarkable activity and stability for the hydrogen evolution reaction. Our experimental results are further understood and supported by theoretical simulations showing that the interstitial nitrogen doping significantly decreases the hydrogen binding energy and lowers the activation barrier for water formation and dissociation.

Development of non-precious metal based oxygen electrocatalysts, particularly bifunctional ones for both oxygen reduction and oxygen evolution is at the heart of electrochemical energy research. Layered double hydroxides have great promise, and to fulfill their full potentials requires effective strategies to engineer and stabilize their structures at the nanoscale. In this study, we report the scalable preparation and delamination of atomic-thick CoNi layered double hydroxide nanosheets, and the subsequent flocculation from their colloidal dispersion upon the introduction of negatively charged graphene oxide nanosheets. Thanks to the large surface areas of CoNi layered double hydroxide monolayers and the high electrical conductivity of reduced graphene oxide support, the thus-formed composite exhibits bifunctional activity and stability far more superior to its close competitors for oxygen reduction and oxygen evolution in both 1 M and 6 M KOH. It could also be used as the oxygen electrocatalyst of rechargeable Zn-air batteries to enable remarkable discharge peak power density and stable cycling stability.

Monodisperse hollow nanostructures have emerged as promising materials for applications in various areas. However, their widespread applications are often hindered by the low efficiency, high cost, and lack of eco-friendliness of existing preparation methods. Here we present a green, robust, efficient, cost-effective and scalable route to monodisperse hollow nanostructures with sodium citrate as the templates. A general precipitation method is developed to prepare uniform and intact salt nanostructures that serve as the green templates for hollow SiO2 nanostructures with controlled size, shape, thickness and porosity. This salt-templated strategy is also extended to the growth of hollow polydopamine nanostructures. We further demonstrate the one-pot synthesis of silica–silver composite nanostructures that exhibit superior performance in the catalytic hydrogenation of 4-nitrophenol.

Background: Drug resistance is a major obstacle in the treatment of non-small cell lung cancer (NSCLC). Recently, miRNAs are reported to be involved in the drug resistance of NSCLC. The roles of miR-124 and miR-142 in the multidrug resistance of NSCLC cells have been reported. However, the underlying mechanism by which miR-124 and miR-142 regulate resistance to cisplatin (CDDP) remains unknown. Methods: The expressions of miR-124, miR-142 and sirtuin 1 (SIRT1) in CDDP-sensitive and CDDP-resistant NSCLC tissues and cells were detected by qRT-PCR and western blot. IC50 value and cell proliferation were determined by MTT assay. Apoptosis was assessed by flow cytometry analysis. Autophagy was evaluated by western blot analysis of the protein levels of LC3-I, LC3-II and p62, and FITC-LC3 punctate formation assay. The interaction between miR-124 or miR-142 and SIRT1 was determined by luciferase reporter, RNA immunoprecipitation (RIP) and western blot assays. A tumor xenograft was performed to further validate the role of miR-124 and miR-142 in the sensitivity of CDDP-resistant NSCLC to cisplatin. Results: miR-124 and miR-142 were downregulated, while SIRT1 was upregulated in CDDP-resistant NSCLC tissues and cells compared to CDDP-sensitive groups. Functionally, overexpression of miR-124 and miR-142 or SIRT1 silencing enhanced the CDDP sensitivity of H1299/CDDP cells via suppressing autophagy, as evidenced by the reduced LC3-II/LC3-I radio, elevated p62 protein, and suppressed FITC-LC3 punctate formation in H1299/CDDP cells. miR-124 and miR-142 were demonstrated to co-target SIRT1. Re-expression of SIRT1 overturned miR-124 and miR-142-mediated chemosensitivity in H1299/CDDP cells via triggering autophagy. Conclusion: miR-124 and miR-142 enhance the cytotoxic effect of CDDP through repressing autophagy via targeting SIRT1 in CDDP-resistant NSCLC cells.

Pd is the only metal that can catalyze electrochemical CO2 reduction to formate at close-to-zero overpotential. It is unfortunately subjected to severe poisoning by trace CO as the side product and suffers from deteriorating stability and selectivity with increasing overpotential. Here, we demonstrate that alloying Pd with Cu in the form of two-dimensional nanodendrites could enable highly stable and selective formate production. Such unique bimetallic nanostructures are formed as a result of the rapid in-plane growth and suppressed out-of-plane growth by carefully controlling a set of experimental parameters. Thanks to the combined electronic effect and nanostructuring effect, our alloy product catalyzes CO2 reduction to formate with remarkable stability and selectivity under the working potential as cathodic as -0.4 V. Our results are rationalized by computational simulations, evidencing that Cu atoms weaken the *CO adsorption and stabilize the *OCHO adsorption on neighboring Pd atoms.

Palladium can enable the electrochemical CO2 reduction to formate with nearly zero overpotential and good selectivity. However, it usually has very limited stability owing to CO poisoning from the side reaction intermediate. Herein, it is demonstrated that alloying palladium with silver is a viable strategy to significantly enhance the electrocatalytic stability. Palladium-silver alloy nanowires are prepared in aqueous solution with tunable chemical compositions, large aspect ratio, and roughened surfaces. Thanks to the unique synergy between palladium and silver, these nanowires exhibit outstanding electrocatalytic performances for selective formate production. Most remarkably, impressive long-term stability is measured even at

Introduction of appropriate cathode electrocatalysts in lithium–sulfur or lithium–polysulfide batteries can accelerate the polysulfide interconversion and suppress the shuttle effect. However, improvements are often limited especially under high sulfur loading. Herein, we prepare molybdenum carbide nanostructures and investigate their potential as the cathode electrocatalyst for lithium–polysulfide batteries. The product is prepared by the self-polymerization of dopamine in the presence of Mo7O246− ions, followed by high-temperature carburization. It features ultrasmall α-MoC1−x nanoparticles uniformly dispersed on a hierarchical carbonaceous support. Polysulfide adsorption experiments and electrochemical measurements show that this material has a strong surface affinity toward polysulfides, and can greatly enhance their conversion rate, in particular the Li2S4 ↔ Li2S2/Li2S conversion. When assessed as the cathode electrocatalyst, it enables lithium–polysulfide batteries with large specific capacity (up to 1400 mA h g−1), impressive rate capability (800 mA h g−1 at 3200 mA g−1) and excellent cycling stability even at high sulfur loading.

The development of Pt-based core/shell nanoparticles represents an emerging class of electrocatalysts for fuel cells, such as methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). Here, we present a one-pot synthesis approach to prepare hexagonal PtBi/Pt core/shell nanostructure composed of an intermetallic Pt1Bi1 core and an ultrathin Pt shell with well-defined shape, size, and composition. The structure and the synergistic effect among different components enhanced their MOR and EOR performance. The optimized Pt2Bi nanoplates exhibit excellent mass activities in both MOR (4,820 mA·mgPt –1) and EOR (5,950 mA·mgPt–1) conducted in alkaline media, which are 6.15 times and 8.63 times higher than those of commercial Pt/C, respectively. Pt2Bi nanoplates also show superior operation durability to commercial Pt/C. This work may inspire the rational design and synthesis of Pt-based nanoparticles with improved performance for fuel cells and other applications.

Alkali metal batteries are now under revival for their large energy density. But their practical viability hinges on the successful development of safe and cyclable alkali metal anodes, preferrentially via scalable and cost-effective methods. Despite tremendous research efforts on the Li metal anode, the attention on Na and K is considerably less. In this work, we report a general and straightforward strategy to enhance the electrochemical performances of Na and K metal anodes. When their surfaces are covered with a thin piece of commercial carbon paper as the protection layer, both Na and K metal anodes exhibit significantly improved overpotentials and cycling stability (up to ~1200 cycles for Na and ~3000 cycles for K) within carbonate or ether electrolyte and even under large current density (5 mA cm−2). Proof-of-concept sodium metal batteries are also assembled using the protected Na metal anode and Na3V2(PO4)3 cathode, and demonstrate large areal capacity and impressive cycle life. Given its effectiveness, scalability and low cost, we believe that our strategy holds great promise for practical implementation.

Transition metal carbide alloys are promising materials to replace platinum as electrodes in electrocatalysts toward the hydrogen evolution reaction (HER). Although tantalum hafnium carbides (Ta-Hf...

The two-electron reduction of molecular oxygen represents an effective strategy to enable the green, mild and on-demand synthesis of hydrogen peroxide. Its practical viability, however, hinges on the development of advanced electrocatalysts, preferably composed of non-precious elements, to selectively expedite this reaction, particularly in acidic medium. Our study here introduces 2H-MoTe2 for the first time as the efficient non-precious-metal-based electrocatalyst for the electrochemical production of hydrogen peroxide in acids. We show that exfoliated 2H-MoTe2 nanoflakes have high activity (onset overpotential ∼140 mV and large mass activity of 27 A g−1 at 0.4 V versus reversible hydrogen electrode), great selectivity (H2O2 percentage up to 93%) and decent stability in 0.5 M H2SO4. Theoretical simulations evidence that the high activity and selectivity of 2H-MoTe2 arise from the proper binding energies of HOO* and O* at its zigzag edges that jointly favor the two-electron reduction instead of the four-electron reduction of molecular oxygen., 2H-MoTe2 nanoflake prepared from liquid phase exfoliation exhibit remarkable electrocatalystic activity for oxygen reduction to hydrogen peroxide in acids.

Mo2C is a possible substitute to Pt-group metals for electrocatalytic hydrogen evolution reaction (HER). Both support-free and carbon-supported Mo2C nanomaterials with improved HER performance have been developed. Herein, distinct from prior research, novel ordered mesoporous core-shell nanowires with Mo2C cores and ultrathin graphitic carbon (GC) shells are rationally synthesized and demonstrated to be excellent for HER. The synthesis is fulfilled via a hard-templating approach combining in situ carburization and localized carbon deposition. Phosphomolybdic acid confined in the SBA-15 template is first converted to MoO2, which is then in situ carburized to Mo2C nanowires with abundant surface defects. Simultaneously, GC layer (the thickness is down to ∼1.0 nm in most areas) is controlled to be locally deposited on the Mo2C surface because of its strong affinity with carbon and catalytic effect on graphitization. Removal of the template results in the Mo2C@GC core-shell nanowire arrays with the structural properties well-characterized. They exhibit excellent performance for HER with a low overpotential of 125 mV at 10 mA cm-2, a small Tafel slope of 66 mV dec-1, and an excellent stability in acidic electrolytes. The influences of several factors, especially the spatial configuration and relative contents of the GC and Mo2C components, on HER performance are elucidated with control experiments. The excellent HER performance of the mesoporous Mo2C@GC core-shell nanowire arrays originates from the rough Mo2C nanowires with diverse active sites and short charge-transfer paths and the ultrathin GC shells with improved surface area, electronic conductivity, and stabilizing effect on Mo2C.

Electrocatalytic carbon dioxide reduction to formate is desirable but challenging. Current attention is mostly focused on tin-based materials, which, unfortunately, often suffer from limited Faradaic efficiency. The potential of bismuth in carbon dioxide reduction has been suggested but remained understudied. Here, we report that ultrathin bismuth nanosheets are prepared from the in situ topotactic transformation of bismuth oxyiodide nanosheets. They process single crystallinity and enlarged surface areas. Such an advantageous nanostructure affords the material with excellent electrocatalytic performance for carbon dioxide reduction to formate. High selectivity (~100%) and large current density are measured over a broad potential, as well as excellent durability for >10 h. Its selectivity for formate is also understood by density functional theory calculations. In addition, bismuth nanosheets were coupled with an iridium-based oxygen evolution electrocatalyst to achieve efficient full-cell electrolysis. When powered by two AA-size alkaline batteries, the full cell exhibits impressive Faradaic efficiency and electricity-to-formate conversion efficiency., The electroreduction of carbon dioxide to liquid products provides an appealing method to convert atmospheric carbon into valuable fuels. Here, the authors perform a topotactic transformation of bismuth oxyiodide to bismuth nanosheets that act as highly selective CO2-to-formate electrocatalysts.

Even though advocated as the potential low-cost alternatives to current lithium-ion technology, the practical viability of sodium-ion batteries remains illusive and depends on the development of high-performance electrode materials. Very few candidates available at present can simultaneously meet the requirements on capacity, rate capability, and cycle life. Herein, we report a high-temperature solution method to prepare Ni3S4 nanorods with uniform sizes. These colloidal nanorods readily self-assemble side by side and form microsized superstructures, which unfortunately negates the nanoscale feature of individual nanorods. To this end, we further introduce two-dimensional graphene nanosheets as the spacer to interrupt nanorod self-assembly. Resultant composite presents a marked advantage toward electrochemical storage of Na+ ions. We demonstrate that in half-cells it exhibits large reversible specific capacity in excess of 600 mAh/g, high rate capability with >300 mAh/g retained at 4 A/g, and great cycle ...

Photoelectrochemical reduction of CO2 to value-added chemicals represents a promising approach for artificial photosynthesis, but often suffers from limited selectivity and stability. Improving its performance would require proper design of semiconductor and co-catalyst materials, along with a strategy for effective coupling. Here, we report that controlled chemical etching of Si wafer by Ag+ ions yields effective semiconductor/co-catalyst interface for photoelectrochemical CO2 reduction. Resultant photocathodes exhibit large photocurrent density (∼10 mA cm−2 under 0.5 sun), great CO faradaic efficiency (90% at −0.5 V versus reversible hydrogen electrode), and impressive operational stability (little activity or selectivity loss within 8 h). Further enhancement (by ∼20%) of photocurrent density is achieved by combining photolithography patterning with chemical etching. Our study applies long-known chemistry as an unexpected solution and may provide a new strategy for high-performance photoelectrochemical CO2 reduction.

Nanocarbon materials recognized as effective and inexpensive catalysts for independent electrochemical reactions, are anticipated to possess a broader spectrum of multifunctionality toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). A rational design of trifunctional nanocarbon catalyst requires balancing the heteroatoms-doping and defect-engineering to afford desired active centers and satisfied electric conductivity, which however is conceptually challenging while desires in-depth research both experimentally and theoretically. This work reports a N,B-codoped graphitic carbon nanocage (NB-CN) with graphitic yet defect-rich characteristic as a promising trifunctional electrocatalyst through a facile thermal pyrolysis assisted in-situ catalytic graphitization (TPCG) process. Density functional theory (DFT) calculations are conducted, for the first time, to demonstrate that the best performance for ORR/OER and HER can be originated from the configuration with B meta to a pyridinic-N, which presents a minimum theoretical overpotential of 0.34 V for ORR, 0.39 V for OER, and a lowest Gibbs free-energy (ΔGads) of 0.013 eV for HER. A primary zinc-air battery is assembled presenting a maximum power density of 320 mW cm−2 along with excellent operation durability, evidencing great potential in practical applications.

Many problems associated with Li–S and Na–S batteries essentially root in the generation of their soluble polysulfide intermediates. While conventional wisdom mainly focuses on trapping polysulfides at the cathode using various functional materials, few strategies are available at present to fully resolve or circumvent this long-standing issue. In this study, we propose the concept of sulfur-equivalent cathode materials, and demonstrate the great potential of amorphous MoS 3 as such a material for room-temperature Li–S and Na–S batteries. In Li–S batteries, MoS 3 exhibits sulfur-like behavior with large reversible specific capacity, excellent cycle life, and the possibility to achieve high areal capacity. Most remarkably, it is also fully cyclable in the carbonate electrolyte under a relatively high temperature of 55 °C. MoS 3 can also be used as the cathode material of even more challenging Na–S batteries to enable decent capacity and good cycle life. Operando X-ray absorption spectroscopy (XAS) experiments are carried out to track the structural evolution of MoS 3 . It largely preserves its chain-like structure during repetitive battery cycling without generating any free polysulfide intermediates.

Summary Electrochemical reduction of CO 2 represents a possible solution for transforming atmospheric CO 2 to value-added chemicals such as CO or hydrocarbons, but so far it has been hampered by the lack of suitable electrocatalysts. In this work, we design a type of organic-inorganic hybrid material by template-directed polymerization of cobalt phthalocyanine on carbon nanotubes for a high-performance CO 2 reduction reaction. Compared with molecular phthalocyanines, the polymeric form of phthalocyanines supported on the conductive scaffold exhibits an enlarged electrochemically active surface area and improved physical and chemical robustness. Experimental results show that our hybrid electrocatalyst can selectively reduce CO 2 to CO with a large faradic efficiency (∼90%), exceptional turnover frequency (4,900 hr −1 at η = 0.5 V), and excellent long-term durability. These metrics are superior to those of most of its organic or inorganic competitors. Its high electrocatalytic activity is also supported by density functional theory calculations.

Porous carbon materials doped with nano-sized transition metal carbides and/or metal-nitrogen coordinative sites are promising oxygen reduction electrocatalysts. The doping of such functionalities in carbon materials with desirable concentration, ultra-small size and stable configuration is still a challenge. In this paper, by grinding and pyrolyzing solid mixtures of an amino acid, an iron salt, and a mesoporous silica template, we demonstrate a solvent-free assembly approach to directly anchor both Fe3C nanoclucters and FeNx sites into nitrogen-doped ordered mesoporous graphitic carbon materials. The carbonaceous electrocatalysts are imparted with several fascinating features, namely, highly dispersed ultra-small Fe3C nanoclusters of 1–3 nm, well-anchored FeNx sites, nitrogen-doped well-graphitized carbon frameworks, and ordered mesopores (∼5.4 nm) and high surface areas (>1000 m2/g), respectively. The combination of these features makes these electrocatalysts exceptional for oxygen reduction reaction under both alkaline and acidic electrolytes, i.e. superior catalytic activities (e.g. onset and half-wave potentials up to 1.00 and 0.89 V vs. the reversible hydrogen electrode in alkaline solution), outstanding stabilities and excellent methanol tolerance, respectively. An in-depth study has been conducted to identify and characterize the key active sites in these electrocatalysts and to elucidate several important influencing factors to optimize the catalytic performance.

To pace with the miniaturization and flexibility tendency of wearable/portable electronics, it is a challenge to develop the lightweight and sustainable power sources with high efficiency. In this work, we proposed an ultralight and flexible self-charging power system via all electrospun paper based triboelectric nanogenerators (EP-TENGs) as energy harvester and all electrospun paper based supercapacitors (EP-SCs) as storage device, respectively. The EP-TENG, made into arch-shape, derived from one nonconductive PAN paper as a triboelectric layer and conductive carbon paper as electrodes. In EP-SC, the conductive carbon paper acted capacitive materials, while the nonconductive PAN paper severed as separator. Therefore, the superiority of the self-charging system is reflected by the properties of these two kinds of papers with lightweight, convenient, low cost, mechanical flexible and tailorable, which were prepared by a simple electrospinning and followed annealing method. When three-parallel EP-TENGs were further integrated with three-series EP-SCs, the all flexible electrospun papers based self-charging power system was constructed. As an effective and innovative power provider, the self-charging system was demonstrated to admirably power an electronic watch and calculator. The proposed self-charging system can be a promising candidate for self-powered wearable electronics and the development of next generation power system in practical applications.

Metal–air batteries have a theoretical energy density that is much higher than that of lithium-ion batteries and are frequently advocated as a solution toward next-generation electrochemical energy storage for applications including electric vehicles or grid energy storage. However, they have not fulfilled their full potential because of challenges associated with the metal anode, air cathode, and electrolyte. These challenges will have to be properly resolved before metal–air batteries can become a practical reality and be deployed on a large scale. Here we survey the current status and latest advances in metal–air battery research for both aqueous (e.g., Zn–air) and nonaqueous (e.g., Li–air) systems. An overview of the general technical issues confronting their development is presented, and our perspective on possible solutions is offered.

Conventional photoelectrochemical cells utilize solar energy to drive the chemical conversion of water or CO2 into useful chemical fuels. Such processes are confronted with general challenges, including the low intrinsic activities and inconvenient storage and transportation of their gaseous products. A photoelectrochemical approach is proposed to drive the reductive production of industrial building-block chemicals and demonstrate that succinic acid and glyoxylic acid can be readily synthesized on Si nanowire array photocathodes free of any cocatalyst and at room temperature. These photocathodes exhibit a positive onset potential, large saturation photocurrent density, high reaction selectivity, and excellent operation durability. They capitalize on the large photovoltage generated from the semiconductor/electrolyte junction to partially offset the required external bias, and thereby make this photoelectrosynthetic approach significantly more sustainable compared to traditional electrosynthesis.

Iron and nitrogen codoped carbons (Fe–N–C) have attracted increasingly greater attention as electrocatalysts for oxygen reduction reaction (ORR). Although challenging, the synthesis of Fe–N–C catalysts with highly dispersed and fully exposed active sites is of critical importance for improving the ORR activity. Here, we report a new type of graphitic Fe–N–C catalysts featuring numerous Fe single atoms anchored on a three-dimensional simple-cubic carbon framework. The Fe–N–C catalyst, derived from self-assembled Fe3O4 nanocube superlattices, was prepared by in situ ligand carbonization followed by acid etching and ammonia activation. Benefiting from its homogeneously dispersed and fully accessible active sites, highly graphitic nature, and enhanced mass transport, our Fe–N–C catalyst outperformed Pt/C and many previously reported Fe–N–C catalysts for ORR. Furthermore, when used for constructing the cathode for zinc–air batteries, our Fe–N–C catalyst exhibited current and power densities comparable to those...

Transition metal carbides are promising electrode materials for electrochemical energy storage, yet to unveil their full potential requires judicious structural engineering at the nanoscale. In this study, we report a chrysanthemum-inspired nanoscale design to prepare a three-dimensional hierarchical molybdenum carbide hybrid. It consisted of an ensemble of numerous nanoflakes protruding out from the center, each formed by ultra-small (∼2 nm) α-MoC1−x nanoparticles uniformly supported on a N-doped carbonaceous support. Such a hybrid material has enlarged surface areas, shortened ionic diffusion length, great mechanical robustness, and buffer room for electrode volume change. Owing to the three-dimensional hierarchical arrangement, this hybrid material exhibits impressive performance toward active lithium-ion storage. It delivers a large reversible capacity of >1000 mA h g−1, great rate capacity with significant capacity at 10 A g−1, and excellent cycling stability with >95% capacity retention after 100 cycles at 500 mA g−1. Most impressively, we demonstrate that the structural integrity of the hybrid microflower is largely preserved even after prolonged cycling.

Nanostructured TiO2 is a promising anode material for Na-ion batteries. In this work, we present a comparative study of anatase and B-phase TiO2 nanowires used for this purpose. We employ X-ray absorption spectroscopy and density functional theory in addition to standard characterization methods to reveal that Na is inserted into both anatase and B-phase nanowires, and that the reversible (de)sodiation capacity is almost the same for both. However the long-term stability of anatase-based Na-ion batteries is poorer than B-phase-based Na-ion batteries. We propose this is due to the irreversible formation of NaxTiO2 near the surface, which blocks Na diffusion. Improved Na-ion battery performance may therefore be obtained using TiO2(B) anodes and by choosing nanostructure geometries with rough surfaces, limiting the unwanted blocking ability of surface barrier layers.

The reversible electrochemical storage of Li+ and Na+ ions is the operating basis of secondary lithium-ion and sodium-ion batteries. In recent years, there has been rapid growth in the search for appropriate electrode materials. Nevertheless, the development of host materials for active and durable electrochemical storage of both Li+ and Na+ ions remain challenging. In this study, we report a facile solvothermal method to prepare hierarchical assemblies of thin SnS2 nanosheets in N-methyl-2-pyrrolidone. The as-prepared product has an expanded layered structure due to the presence of organic intercalates. Mild annealing restores the normal 2H-SnS2 phase with the hierarchical architecture preserved. When annealed SnS2 was evaluated as the anode material of lithium-ion batteries, it exhibited large capacity in excess of 1200 mA h g−1 and decent short-term cycling stability. It was further coated with a thin carbon layer as the physical and electrical reinforcement, which led to a much improved cycle life at both low and high current rates. Moreover, carbon coated SnS2 also demonstrated a large capacity (∼600 mA h g−1) and decent cycling stability as the anode material of sodium-ion batteries.

Formic acid (or formate) is suggested to be one of the most economically viable products from electrochemical carbon dioxide reduction. However, its commercial viability hinges on the development of highly active and selective electrocatalysts. Here we report that structural defects have a profound positive impact on the electrocatalytic performance of bismuth. Bismuth oxide double-walled nanotubes with fragmented surface are prepared as a template, and are cathodically converted to defective bismuth nanotubes. This converted electrocatalyst enables carbon dioxide reduction to formate with excellent activity, selectivity and stability. Most significantly, its current density reaches ~288 mA cm−2 at −0.61 V versus reversible hydrogen electrode within a flow cell reactor under ambient conditions. Using density functional theory calculations, the excellent activity and selectivity are rationalized as the outcome of abundant defective bismuth sites that stabilize the *OCHO intermediate. Furthermore, this electrocatalyst is coupled with silicon photocathodes and achieves high-performance photoelectrochemical carbon dioxide reduction., Carbon dioxide can be electrochemically reduced to form valuable chemical feedstocks, but efficiency of electrocatalysts should be improved. Here the authors report nanotube-derived bismuth for electrocatalytic reduction of carbon dioxide to formate, with performance that is enhanced by defects.

The development of nonprecious metal based electrocatalysts for hydrogen evolution reaction (HER) has received increasing attention over recent years. Previous studies have established Mo2C as a promising candidate. Nevertheless, its preparation requires high reaction temperature, which more than often causes particle sintering and results in low surface areas. In this study, we show supporting Mo2C nanoparticles on the three-dimensional scaffold as a possible solution to this challenge and develop a facile two-step preparation method for ∼3 nm Mo2C nanoparticles uniformly dispersed on carbon microflowers (Mo2C/NCF) via the self-polymerization of dopamine. The resulting hybrid material possesses large surface areas and a fully open and accessible structure with hierarchical order at different levels. MoO42– was found to play an important role in inducing the formation of this morphology presumably via its strong chelating interaction with the catechol groups of dopamine. Our electrochemical evaluation dem...

Earlier research has been primarily focused on WC as one of the most promising earth-abundant electrocatalysts for hydrogen evolution reaction (HER), whereas the other compound in this carbide family—W2C—has received far less attention. Our theoretical calculations suggest that such a focus is misplaced and W2C is potentially more HER-active than WC. Nevertheless, the preparation of phase pure and sintering-free W2C nanostructures represents a formidable challenge. Here we develop an improved carburization method and successfully prepare ultrasmall and phase-pure W2C nanoparticles. When evaluated for HER electrocatalysis, W2C nanoparticles exhibit a small onset overpotential of 50 mV, a Tafel slope of 45 mV dec−1 and outstanding long-term cycling stability, which are dramatically improved over all existing WC-based materials. In addition, the integration of W2C nanoparticles with p-type Si nanowires enables highly active and sustainable solar-driven hydrogen production. Our results highlight the great potential of this traditionally non-popular material in HER electrocatalysis. Tungsten carbide has yet to live up to its long-believed potential as a replacement for precious metal electrocatalysts. Here, Li and co-workers demonstrate that ditungsten carbide in the form of ultrasmall, phase-pure nanoparticles is a better candidate for the hydrogen evolution reaction.

Nanostructured metal sulfides are potential electrode materials for sodium-ion batteries; however, they typically suffer from very poor cycling stability due to large volume changes and dissolution of discharge products. Herein we propose a rational material design strategy for sulfide-based materials to address these problems. Taking nickel sulfide (NiS x ) as an example, we demonstrated that its electrochemical performance can be dramatically improved by confining the NiSx nanoparticles in a percolating conductive carbon nanotube network, and stabilizing them with an ultrathin carbon coating layer. The carbon layer serves as a physical barrier to alleviate the effects of both the volume change and dissolution of active materials. The hybrid material exhibited a large reversible specific capacity of >500 mAh/g and excellent cycling stability over 200 cycles. Given the traditionally problematic nature of NiS x as a battery anode material, we believe that the observed high performance reported here reflects the effectiveness of our material design strategy.