Mo-doping heterojunction: interfacial engineering in an efficient electrocatalyst for superior simulated seawater hydrogen evolution.

Exploring economical, efficient, and stable electrocatalysts for the seawater hydrogen evolution reaction (HER) is highly desirable but is challenging. In this study, a Mo cation doped Ni0.85Se/MoSe2 heterostructural electrocatalyst, Mox-Ni0.85Se/MoSe2, was successfully prepared by simultaneously doping Mo cations into the Ni0.85Se lattice (Mox-Ni0.85Se) and growing atomic MoSe2 nanosheets epitaxially at the edge of the Mox-Ni0.85Se. Such an Mox-Ni0.85Se/MoSe2 catalyst requires only 110 mV to drive current densities of 10 mA cm-2 in alkaline simulated seawater, and shows almost no obvious degradation after 80 h at 20 mA cm-2. The experimental results, combined with the density functional theory calculations, reveal that the Mox-Ni0.85Se/MoSe2 heterostructure will generate an interfacial electric field to facilitate the electron transfer, thus reducing the water dissociation barrier. Significantly, the heteroatomic Mo-doping in the Ni0.85Se can regulate the local electronic configuration of the Mox-Ni0.85Se/MoSe2 heterostructure catalyst by altering the coordination environment and orbital hybridization, thereby weakening the bonding interaction between the Cl and Se/Mo. This synergistic effect for the Mox-Ni0.85Se/MoSe2 heterostructure will simultaneously enhance the catalytic activity and durability, without poisoning or corrosion of the chloride ions.

Atomically dispersed Fe-O4-C sites as efficient electrocatalysts for electrosynthesis of hydrogen peroxide.

The electrochemical reduction of oxygen via the 2e pathway is an environmentally friendly approach to the electrosynthesis of H2O2. Nevertheless, its sluggish kinetics and limited selectivity hinder its practical application. Herein, single Fe atoms anchored on graphene oxide (SA Fe/GO) with Fe-O4-C sites are developed as an efficient electrocatalyst for the electro-synthesis of H2O2. These Fe-O4-C site active centres could efficiently enhance the activity and selectivity towards 2e electrochemical oxygen reduction in an alkaline environment. The newly-developed SA Fe/GO electrocatalyst demonstrates exceptional electrochemical performance, exhibiting impressive activity with an onset potential of 0.90 and H2O2 production of 0.60 mg cm-2 h-1 at 0.4 V. Remarkably, it achieves a remarkable H2O2 selectivity of over 95.5%.

Cation-Tuning Engineering on Metal Oxides for Oxygen Electrocatalysis.

Cation-tuning engineering has become a new frontier in altering the electronic structure of electrocatalysts, which has been employed to enhance their electrochemical performance. Significant efforts have been made to promote the electrochemical performance of transition metal-based materials during oxygen electrocatalysis and related energy devices such as Zn-air batteries. Herein, the advantages of cation-tuning engineering, including cation vacancies/defects and cation doping, in the modification of the electronic structure of transition metal oxide catalysts are discussed. Additionally, practical applications of the cation-tuning engineering strategy are reviewed in detail with a special emphasis on oxygen reduction reaction and oxygen evolution reaction. Lastly, challenges and future opportunities in this field are also proposed.

Atomically Dispersed Dual-Site Cathode with a Record High Sulfur Mass Loading for High-Performance Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur (RT-Na/S) batteries possess high potential for grid-scale stationary energy storage due to their low cost and high energy density. However, the issues arising from the low S mass loading and poor cycling stability caused by the shuttle effect of polysulfides seriously limit their operating capacity and cycling capability. Herein, sulfur-doped graphene frameworks supporting atomically dispersed 2H-MoS2 and Mo1 (S@MoS2 -Mo1 /SGF) with a record high sulfur mass loading of 80.9 wt.% are synthesized as an integrated dual active sites cathode for RT-Na/S batteries. Impressively, the as-prepared S@MoS2 -Mo1 /SGF display unprecedented cyclic stability with a high initial capacity of 1017 mAh g-1 at 0.1 A g-1 and a low-capacity fading rate of 0.05% per cycle over 1000 cycles. Experimental and computational results including X-ray absorption spectroscopy, in situ synchrotron X-ray diffraction and density-functional theory calculations reveal that atomic-level Mo in this integrated dual-active-site forms a delocalized electron system, which could improve the reactivity of sulfur and reaction reversibility of S and Na, greatly alleviating the shuttle effect. The findings not only provide an effective strategy to fabricate high-performance dual-site cathodes, but also deepen the understanding of their enhancement mechanisms at an atomic level.

Elastic Lattice Enabling Reversible Tetrahedral Li Storage Sites in a High-Capacity Manganese Oxide Cathode.

The key to breaking through the capacity limitation imposed by intercalation chemistry lies in the ability to harness more active sites that can reversibly accommodate more ions (e.g., Li+ ) and electrons within a finite space. However, excessive Li-ion insertion into the Li layer of layered cathodes results in fast performance decay due to the huge lattice change and irreversible phase transformation. In this study, an ultrahigh reversible capacity is demonstrated by a layered oxide cathode purely based on manganese. Through a wealth of characterizations, it is clarified that the presence of low-content Li2 MnO3 domains not only reduces the amount of irreversible O loss; but also regulates Mn migration in LiMnO2 domains, enabling elastic lattice with high reversibility for tetrahedral sites Li-ion storage in Li layers. This work utilizes bulk cation disorder to create stable Li-ion-storage tetrahedral sites and an elastic lattice for layered materials, with a reversible capacity of 600 mA h g-1 , demonstrated in th range 0.6-4.9 V versus Li/Li+ at 10 mA g-1 . Admittedly, discharging to 0.6 V might be too low for practical use, but this exploration is still of great importance as it conceptually demonstrates the limit of Li-ions insertion into layered oxide materials.

Highly efficient and selective electrocatalytic hydrogen peroxide production on Co-O-C active centers on graphene oxide.

Electrochemical oxygen reduction provides an eco-friendly synthetic route to hydrogen peroxide (H2O2), a widely used green chemical. However, the kinetically sluggish and low-selectivity oxygen reduction reaction (ORR) is a key challenge to electrochemical production of H2O2 for practical applications. Herein, we demonstrate that single cobalt atoms anchored on oxygen functionalized graphene oxide form Co-O-C@GO active centres (abbreviated as Co1@GO for simplicity) that act as an efficient and durable electrocatalyst for H2O2 production. This Co1@GO electrocatalyst shows excellent electrochemical performance in O2-saturated 0.1 M KOH, exhibiting high reactivity with an onset potential of 0.91 V and H2O2 production of 1.0 mg cm-2 h-1 while affording high selectivity of 81.4% for H2O2. Our combined experimental observations and theoretical calculations indicate that the high reactivity and selectivity of Co1@GO for H2O2 electrogeneration arises from a synergistic effect between the O-bonded single Co atoms and adjacent oxygen functional groups (C-O bonds) of the GO present in the Co-O-C active centres.

Room temperature liquid metals for flexible alkali metal-chalcogen batteries.

Flexibility has become a certain trend in the development of secondary batteries to meet the requirements of wide portability and applicability. On account of their intrinsic high energy density, flexible alkali metal-chalcogen batteries are attracting increasing interest. Although great advances have been made in promoting the electrochemical performance of metal-S or metal-Se batteries, explorations on flexible chalcogen-based batteries are still limited. Extensive and rational use of soft materials for electrodes is the main bottleneck. The re-emergence of safe liquid metals (LMs), which provide an ideal combination of metallic and fluidic properties at room temperature, offers a fascinating paradigm for constructing flexible chalcogen batteries. They may provide dendrite-free anodes and restrain the dissolution of polysulfides and polyselenides for cathodes. From this perspective, we elaborate on the appealing features of LMs for the construction of flexible metal-chalcogen batteries. Recent advances on LM-based battery are discussed, covering novel liquid alkali metals as anodes and LM-sulfur hybrids as cathodes, with the focus placed on durable high-energy-density output and self-healing flexible capability. At last, perspectives are proposed on the future development of LM-based chalcogen batteries, and the viable strategies to meet the current challenges that are obstructing more practical flexible chalcogen batteries.

Bi-Atom Electrocatalyst for Electrochemical Nitrogen Reduction Reactions.

The electrochemical nitrogen reduction reaction (NRR) to directly produce NH3 from N2 and H2O under ambient conditions has attracted significant attention due to its ecofriendliness. Nevertheless, the electrochemical NRR presents several practical challenges, including sluggish reaction and low selectivity. Here, bi-atom catalysts have been proposed to achieve excellent activity and high selectivity toward the electrochemical NRR by Ma and his co-workers. It could accelerate the kinetics of N2-to-NH3 electrochemical conversion and possess better electrochemical NRR selectivity. This work sheds light on the introduction of bi-atom catalysts to enhance the performance of the electrochemical NRR.

Atomic Structural Evolution of Single-Layer Pt Clusters as Efficient Electrocatalysts.

The rational synthesis of single-layer noble metal directly anchored on support materials is an elusive target to accomplish for a long time. This paper reports well-defined single-layer Pt (Pt-SL) clusters anchored on ultrathin TiO2 nanosheets-as a new frontier in electrocatalysis. The structural evolution of Pt-SL/TiO2 via self-assembly of single Pt atoms (Pt-SA) is systematically recorded. Significantly, the Pt atoms of Pt-SL/TiO2 possess a unique electronic configuration with PtPt covalent bonds surrounded by abundant unpaired electrons. This Pt-SL/TiO2 catalyst presents enhanced electrochemical performance toward diverse electrocatalytic reactions (such as the hydrogen evolution reaction and the oxygen reduction reaction) compared with Pt-SA, multilayer Pt nanoclusters, and Pt nanoparticles, suggesting an efficient new type of catalyst that can be achieved by constructing single-layer atomic clusters on supports.

Long-Life Room-Temperature Sodium-Sulfur Batteries by Virtue of Transition-Metal-Nanocluster-Sulfur Interactions.

Room-temperature sodium-sulfur (RT-Na/S) batteries hold significant promise for large-scale application because of low cost of both sodium and sulfur. However, the dissolution of polysulfides into the electrolyte limits practical application. Now, the design and testing of a new class of sulfur hosts as transition-metal (Fe, Cu, and Ni) nanoclusters (ca. 1.2 nm) wreathed on hollow carbon nanospheres (S@M-HC) for RT-Na/S batteries is reported. A chemical couple between the metal nanoclusters and sulfur is hypothesized to assist in immobilization of sulfur and to enhance conductivity and activity. S@Fe-HC exhibited an unprecedented reversible capacity of 394 mAh g-1 despite 1000 cycles at 100 mA g-1 , together with a rate capability of 220 mAh g-1 at a high current density of 5 A g-1 . DFT calculations underscore that these metal nanoclusters serve as electrocatalysts to rapidly reduce Na2 S4 into short-chain sulfides and thereby obviate the shuttle effect.

Atomic cobalt as an efficient electrocatalyst in sulfur cathodes for superior room-temperature sodium-sulfur batteries.

The low-cost room-temperature sodium-sulfur battery system is arousing extensive interest owing to its promise for large-scale applications. Although significant efforts have been made, resolving low sulfur reaction activity and severe polysulfide dissolution remains challenging. Here, a sulfur host comprised of atomic cobalt-decorated hollow carbon nanospheres is synthesized to enhance sulfur reactivity and to electrocatalytically reduce polysulfide into the final product, sodium sulfide. The constructed sulfur cathode delivers an initial reversible capacity of 1081 mA h g-1 with 64.7% sulfur utilization rate; significantly, the cell retained a high reversible capacity of 508 mA h g-1 at 100 mA g-1 after 600 cycles. An excellent rate capability is achieved with an average capacity of 220.3 mA h g-1 at the high current density of 5 A g-1. Moreover, the electrocatalytic effects of atomic cobalt are clearly evidenced by operando Raman spectroscopy, synchrotron X-ray diffraction, and density functional theory.

In Situ Grown S Nanosheets on Cu Foam: An Ultrahigh Electroactive Cathode for Room-Temperature Na-S Batteries.

Room-temperature sodium-sulfur batteries are competitive candidates for large-scale stationary energy storage because of their low price and high theoretical capacity. Herein, pure S nanosheet cathodes can be grown in situ on three-dimensional Cu foam substrate with the condensation between binary polymeric binders, serving as a model system to investigate the formation and electrochemical mechanism of unique S nanosheets on the Cu current collectors. On the basis of the confirmed conversion reactions to Na2S, The constructed cathode exhibits ultrahigh initial discharge/charge capacity of 3189/1403 mAh g-1. These results suggest that there is great potential to optimize S cathode by exploiting low-cost Cu substrates instead of conventional Al current collectors.

Puerariae Lobatae Radix elevated expression levels of OB-R, IRS2, GLUT1 and GLUT2 to regulate glucose metabolism in insulin-resistance HepG2 cells / 中国中药杂志

To observe the anti-hyperglycemic effect of Puerariae Lobatae Radix in hepatocyte insulin resistance(IR) models, and investigate its preliminary molecular mechanism. IR-HepG2 cell model was stably established with 1×10-9 mol•L⁻¹ insulin plus 3.75×10-6 mol•L-1 dexamethasone treatment for 48 h according to optimized protocol in our research group. After IR-HepG2 cells were treated with different concentrations(5%,10% and 15%) of Puerariae Lobatae Radix-containing serum, cell viability was detected by CCK-8 assay; the glucose consumptions in IR-HepG2 cells were separately detected at different time points (12, 15, 18, 21, 24, 30, 36 h) by using glucose oxidase method; intracellular glycogen content was detected by anthrone method; and the protein expression levels of leptin receptor (Ob-R), insulin receptor substrate-2 (IRS2), glucose transporter 1(GLUT1) and GLUT2 were detected by Western blot assay. The results showed that Puerariae Lobatae Radix-containing serum (5%, 10% and 15%) had no significant effect on IR-HepG2 cell viability; 5% and 10% Puerariae Lobatae Radix-containing serum significantly increased glucose consumption of IR-HepG2 cells (P<0.01) at 18, 21 and 24 h; 15% Puerariae Lobatae Radix-containing serum elevated the glucose consumption of IR-HepG2 cells at 15 h (P<0.05), and significantly elevated the glucose consumption at 18, 21, 24 and 30 h (P<0.01) in a dose-dependent manner. The optimized time of anti-hyperglycemic effect was defined as 24 h, and further study showed that Puerariae Lobatae Radix-containing serum could increase intracellular glycogen content after 24 h treatment (P<0.01), and up-regulate IRS2, Ob-R, GLUT1 and GLUT2 protein expression levels. Our results indicated that Puerariae Lobatae Radix-containing serum could achieve the anti-hyperglycemic effect through important PI3K/PDK signaling pathway partially by up-regulating the expression levels of Ob-R and IRS2, GLUT1 and GLUT2 in IR-HepG2 cells, accelerating the glucose transport into hepatocytes and increasing hepatic glycogen synthesis to enhance the anti-hyperglycemic effect of IR-HepG2 cells.

High activity of cubic PtRh alloys supported on graphene towards ethanol electrooxidation.

Cubic PtRh alloys supported on graphene (PtxRhy/GN) with different atomic ratio of Pt and Rh were directly synthesized for the first time using the modified polyol method with Br(-) for the shape-directing agents. The process didn't use surface-capping agents such as PVP that easily occupy the active sites of electrocatalysts and are difficult to remove. Graphene is the key factor for cubic shape besides Br(-) and keeping catalysts high-dispersed. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the structure and morphology of these electrocatalysts. The results showed that they were composed of homogeneous cubic PtRh alloys. Traditional electrochemical methods, such as cyclic voltammetry and chronoamperometry, were used to investigate the electrocatalytic properties of PtxRhy/GN towards ethanol electrooxidation. It can be seen that PtxRhy/GN with all atomic ratios exhibited high catalytic activity, and the most active one has a composition with Pt : Rh = 9 : 1 atomic ratio. Electrochemical in situ FTIR spectroscopy was used to evaluate the cleavage of C-C bond in ethanol at room temperature in acidic solutions, the results illustrated that Rh in an alloy can promote the split of C-C bond in ethanol, and the alloy catalyst with atomic ratio Pt : Rh = 1 : 1 showed obviously better performance for the C-C bond breaking in ethanol and higher selectivity for the enhanced activity of ethanol complete oxidation to CO2 than alloys with other ratios of Pt and Rh. The investigation indicates that high activity of PtxRhy/GN electrocatalyst towards ethanol oxidation is due to the specific shape of alloys and the synergistic effect of two metal elements as well as graphene support.