Construction of Co-Se-W at Interfaces of Phase-Mixed Cobalt Selenide via Spontaneous Phase Transition for Platinum-Like Hydrogen Evolution Activity and Long-Term Durability in Alkaline and Acidic Media.

Cost-effective transition metal chalcogenides are highly promising electrocatalysts for both alkaline and acidic hydrogen evolution reactions (HER). However, unsatisfactory HER kinetics and stability have severely hindered their applications in industrial water electrolysis. Herein, a nanoflowers-shaped W-doped cubic/orthorhombic phase-mixed CoSe2 catalyst ((c/o)-CoSe2-W) is reported. The W doping induces spontaneous phase transition from stable phase cubic CoSe2 (c-CoSe2) to metastable phase orthorhombic CoSe2, which not only enables precise regulation of the ratio of two phases but also realizes W doping at the interfaces of two phases. The (c/o)-CoSe2-W catalyst exhibits a Pt-like HER activity in both alkaline and acidic media, with record-low HER overpotentials of 29.8 mV (alkaline) and 35.9 mV (acidic) at 10 mA cm-2, respectively, surpassing the vast majority of previously reported non-precious metal electrocatalysts for both alkaline and acidic HER. The Pt-like HER activities originate from the formation of Co-Se-W active species on the c-CoSe2 side at the phase interface, which effectively modulates electron structures of active sites, not only enhancing H2O adsorption and dissociation at Co sites but also optimizing H* adsorption to ΔGH* ≈ 0 at W sites. Benefiting from the abundant phase interfaces, the catalyst also displays outstanding long-term durability in both acidic and alkaline media.

Amorphous/Crystalline Phases Mixed Nanosheets Array Rich in Oxygen Vacancies Boost Oxygen Evolution Reaction of Spinel Oxides in Alkaline Media.

As promising oxygen evolution reaction (OER) catalysts, spinel-type oxides face the bottleneck of weak adsorption for oxygen-containing intermediates, so it is challenging to make a further breakthrough in remarkably lowering the OER overpotential. In this study, a novel strategy is proposed to substantially enhance the OER activity of spinel oxides based on amorphous/crystalline phases mixed spinel FeNi2O4 nanosheets array, enriched with oxygen vacancies, in situ grown on a nickel foam (NF). This unique architecture is achieved through a one-step millisecond laser direct writing method. The presence of amorphous phases with abundant oxygen vacancies significantly enhances the adsorption of oxygen-containing intermediates and changes the rate-determining step from OH*→O* to O*→OOH*, which greatly reduces the thermodynamic energy barrier. Moreover, the crystalline phase interweaving with amorphous domains serves as a conductive shortcut to facilitate rapid electron transfer from active sites in the amorphous domain to NF, guaranteeing fast OER kinetics. Such an anodic electrode exhibits a nearly ten fold enhancement in OER intrinsic activity compared to the pristine counterpart. Remarkably, it demonstrates record-low overpotentials of 246 and 315 mV at 50 and 500 mA cm-2 in 1 m KOH with superior long-term stability, outperforming other NiFe-based spinel oxides catalysts.

In-situ construction of cation vacancies in amphoteric-metallic element-doped NiFe-LDH as ultrastable and efficient alkaline hydrogen evolution electrocatalysts at 1000 mA cm-2.

Developing efficient and stable electrocatalysts at affordable costs is very important for large-scale production of green hydrogen. In this study, unique amphoteric metallic element-doped NiFe-LDH nanosheet arrays (NiFeCd-LDH, NiFeZn-LDH and NiFeAl-LDH) using as high-performance bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were reported, by tuning electronic structure and vacancy engineering. It was found that NiFeCd-LDH possesses the lowest overpotentials of 85 mV and 240 mV (at 10 mA cm-2) for HER and OER, respectively. Density functional theory (DFT) calculations reveal the synergistic effect of Cd vacancies and Cd doping on improving alkaline HER performance, which promote the achievement of excellent catalytic activity and ultrastable hydrogen production at a large current density of 1000 mA cm-2 within 250 h. Besides, the overall water splitting performance of the as-prepared NiFeCd-LDH requires only 1.580 V to achieve a current density of 10 mA cm-2 in alkaline seawater media, underscoring the importance of modifying the electronic properties of LDH for efficient overall water splitting in both alkaline water/seawater environments.

A Strongly Coupled Ag(S)@NiO/Nickel Foam Electrode Induced by Laser Direct Writing for Hydrogen Evolution at Ultrahigh Current Densities with Long-Term Durability.

Highly active, durable, and cost-effective electrodes for hydrogen evolution reaction (HER) at ultrahigh current densities (≥1 A cm-2 ) are extremely demanded for industrial high-rate hydrogen production, but challenging. Here, a robust strongly coupled Ag(S)@NiO/nickel foam (NF) electrode is reported. Taking advantage of millisecond laser direct writing in liquid nitrogen technique, lattice-matched and coherent interfaces are formed between Ag nanoparticles with stacking faults (denoted by Ag(S)) and NiO nanosheets, leading to strong interfacial electronic coupling, not only promoting H2 O adsorption and dissociation on Ni2+ but also enhancing H* adsorption on intrinsically inactive but most electrically conductive Ag. Strong chemical bonding is established at NiO/NF interface, guaranteeing rapid electron transfer and excellent mechanical durability under high-rate hydrogen evolution. The physicochemically stable electrode achieves record-low alkaline HER overpotential of 167 and 180 mV at 1 and 1.5 A cm-2 , respectively, along with negligible activity decay after 120 h test at ≈1.5 A cm-2 , surpassing reported non-platinum group metal electrocatalysts.

Ag-doped Cu nanosheet arrays for efficient hydrogen evolution reaction.

A zinc-infiltration process was adopted to prepare silver-doped copper nanosheet arrays. The larger atomic radius of Ag introduces tensile stress, which lowers the electron density at the s-orbitals of Cu atoms and improves the adsorption capability for hydrogen atoms. As a catalyst for hydrogen evolution, these silver doped copper nanosheet arrays achieved a low overpotential of 103 mV at 10 mA cm-2 in 1 M KOH, which is 604 mV lower than that of pure copper foil.

Photothermal-enabled single-atom catalysts for high-efficiency hydrogen peroxide photosynthesis from natural seawater.

Hydrogen peroxide (H2O2) is a powerful industrial oxidant and potential carbon-neutral liquid energy carrier. Sunlight-driven synthesis of H2O2 from the most earth-abundant O2 and seawater is highly desirable. However, the solar-to-chemical efficiency of H2O2 synthesis in particulate photocatalysis systems is low. Here, we present a cooperative sunlight-driven photothermal-photocatalytic system based on cobalt single-atom supported on sulfur doped graphitic carbon nitride/reduced graphene oxide heterostructure (Co-CN@G) to boost H2O2 photosynthesis from natural seawater. By virtue of the photothermal effect and synergy between Co single atoms and the heterostructure, Co-CN@G enables a solar-to-chemical efficiency of more than 0.7% under simulated sunlight irradiation. Theoretical calculations verify that the single atoms combined with heterostructure significantly promote the charge separation, facilitate O2 absorption and reduce the energy barriers for O2 reduction and water oxidation, eventually boosting H2O2 photoproduction. The single-atom photothermal-photocatalytic materials may provide possibility of large-scale H2O2 production from inexhaustible seawater in a sustainable way.

Surface-Dependent Hydrogen Evolution Activity of Copper Foil.

Single-crystal planes are ideal platforms for catalytic research. In this work, rolled copper foils with predominantly (220) planes were used as the starting material. By using temperature gradient annealing, which caused grain recrystallization in the foils, they were transformed to those with (200) planes. In acidic solution, the overpotential of such a foil (10 mA cm-2) was found to be 136 mV lower than that of a similar rolled copper foil. The calculation results show that hollow sites formed on the (200) plane have the highest hydrogen adsorption energy and are active centers for hydrogen evolution. Thus, this work clarifies the catalytic activity of specific sites on the copper surface and demonstrates the critical role of surface engineering in designing catalytic properties.

Ion Solvation Free Energy Calculation Based on Ab Initio Molecular Dynamics Using a Hybrid Solvent Model.

Free energy calculation of small molecules or ion species in aqueous solvent is one of the most important problems in electrochemistry study. Although there are many previous approaches to calculate such free energies, they are based on ab initio methods and suffer from various limitations and approximations. In the current work, we developed a hybrid approach based on ab initio molecular dynamics (AIMD) simulations to calculate the ion solvation energy. In this approach, a small water cluster surrounding the central ion is used, and implicit solvent model is applied outside the water cluster. A dynamic potential well is used during AIMD to keep the water cluster together. Quasi-harmonic approximation is used to calculate the entropy contribution, while the total energy average is used to calculate the enthalpy term. The obtained solvation voltages of the bulk metal agree with experiments within 0.3 eV, and the simulation results for the solvation energies of gaseous ions are close to the experimental observations. Besides the free energies, radial pair distribution functions and coordination numbers of hydrated cations are also obtained. The remaining challenges of this method are also discussed.

Regulating the work function of silver catalysts via surface engineering for enhanced CO2 electroreduction.

The work function can serve as a characteristic quantity to evaluate the catalytic activity due to its relationship with the surface structure of a material. However, what factors determine the influence of the work function on the electrochemical performance are still unclear. Herein, we elucidate the effect of the work function of Ag on the electrochemical reduction of CO2 to CO by controlling the ratio of exposed crystalline planes. To this end, the exposed surface of Ag powder was regulated by high-energy ball milling and its influence on CO2 reduction was investigated. The surface structure with more Ag(110) surface achieves higher activity and selectivity for CO production, resulting from the lower work function of Ag(110), which dramatically enhances the electron tunnelling probability during CO2 electroreduction. We found that a higher ratio of Ag(110) to Ag(100) leads to a lower work function and thus better electrochemical activity and selectivity. This study demonstrates a promising strategy to enhance the electrochemical performance of metal catalysts through tuning their work functions via regulating exposed crystalline planes.

Sulfate-Enabled Nitrate Synthesis from Nitrogen Electrooxidation on a Rhodium Electrocatalyst.

The electrocatalytic nitrogen oxidation reaction (NOR) to generate nitrate is gaining increasing attention as an alternative approach to the conventional industrial manufacture. But, current progress in NOR is limited by the difficulties in activation and conversion of the strong N≡N bond (941 kJ mol-1 ). Herein, we designed to utilize sulfate to enhance NOR performance over an Rh electrocatalyst. After the addition of sulfate, the inert Rh nanoparticles exhibited superior NOR performance with a nitrate yield of 168.0 µmol gcat -1 h-1 . The 15 N isotope-labeling experiment confirmed the produced nitrate from nitrogen electrooxidation. A series of electrochemical in situ characterizations and theoretical calculation unveiled that sulfate promoted nitrogen adsorption and decreased the reaction energy barrier, and in situ formed sulfate radicals reduced the activation energy of the potential-determining step, thus accelerating NOR.

Exposing Cu(100) Surface via Ion-Implantation-Induced Oxidization and Etching for Promoting Hydrogen Evolution Reaction.

Metallic materials with unique surface structure have attracted much attention due to their unique physical and chemical properties. However, it is hard to prepare bulk metallic materials with special crystal faces, especially at the nanoscale. Herein, we report an efficient method to adjust the surface structure of a Cu plate which combines ion implantation technology with the oxidation-etching process. The large number of vacancies generated by ion implantation induced the electrochemical oxidation of several atomic layers in depth; after chemical etching, the Cu(100) planes were exposed on the surface of the Cu plate. As a catalyst for acid hydrogen evolution reaction, the Cu plate with (100) planes merely needs 273 mV to deliver a current density of 10 mA/cm2 because the high-energy (100) surface has moderate hydrogen adsorption and desorption capability. This work provides an appealing strategy to engineer the surface structure of bulk metallic materials and improve their catalytic properties.

Surface Valence State Effect of MoO2+x on Electrochemical Nitrogen Reduction.

The valance of Mo is critical for FeMo cofactor in ambient ammonia synthesis. However, the valence effect of Mo has not been well studied in heterogeneous nanoparticle catalysts for electrochemical nitrogen reduction reaction (NRR) due to the dissolution of Mo as MoO42- in alkaline electrolytes. Here, a MoO2+x catalyst enriched with surface Mo6+ is reported. The Mo6+ is stabilized by a native oxide layer to prevent corrosion and its speciation is identified as (MoO3 )n clusters. This native layer with Mo6+ suppresses the hydrogen evolution significantly and promotes the activation of nitrogen as supported by both experimental characterization and theoretical calculation. The as-prepared MoO2+x catalyst shows a high ammonia yield of 3.95 µg mgcat-1 h-1 with a high Faradaic efficiency of 22.1% at -0.2 V versus reversible hydrogen electrode, which is much better than the MoO2 catalyst with Mo6+ etched away. The accuracy of experimental results for NRR is confirmed by various control experiments and quantitative isotope labeling.

A silver catalyst with a high-energy surface prepared by plasma spraying for the hydrogen evolution reaction.

A self-supported silver electrode was prepared by plasma spraying and used for catalysing the hydrogen evolution reaction. Thanks to the non-equilibrium synthetic conditions, the silver catalyst exposes high-energy (200) crystal planes, which enhance the adsorption of hydrogen and improve the intrinsic catalytic activity. As a result, the silver catalyst delivers an overpotential of 349 mV at 10 mA cm-2, which was much lower than those of Ag foil (742 mV) and commercial Ag powder (657 mV). This work provides a new idea of preparing active electrocatalysts by traditional processes.

Highly Conjugated Graphitic Carbon Nitride Nanofoam for Photocatalytic Hydrogen Evolution.

As a metal-free photocatalyst, graphitic carbon nitride (g-CN) shows great potential for photocatalytic water splitting, although its performance is significantly limited by structural defects due to incomplete polymerization. In the present work, we successfully synthesize highly conjugated g-CN nanofoam through an iodide substitution technique. The product possesses a high polymerization degree, low defect density, and large specific surface area; as a result, it achieves a hydrogen evolution rate of 9.06 mmol h-1 g-1 under visible light irradiation, with an apparent quantum efficiency (AQE) of 18.9% at 420 nm. Experimental analysis and theoretical calculations demonstrate that the recombination of photogenerated carriers at C-NHx defects was effectively depressed in the nanofoam, giving rise to the high photocatalytic activity.

Epitaxial Growth of High-Energy Copper Facets for Promoting Hydrogen Evolution Reaction.

Copper is known as a conductive metal but an inert catalyst for the hydrogen evolution reaction due to its inappropriate electronic structure. In this work, an active copper catalyst is prepared with high-energy surfaces by adopting the friction stir welding (FSW) technique. FSW can mix the immiscible Fe and Cu materials homogenously and heat them to a high temperature. Resultantly, α-Fe transforms into γ-Fe, and low-energy γ-Fe (100) and (110) surfaces induce the epitaxial growth of high-energy Cu (110) and (100) planes, respectively. After the removal of γ-Fe by acid etching, the copper electrode exposes high-energy surface and exhibits excellent acidic HER activity, even being superior to Pt foil at high current densities (>66 mA cm-2 ). Density functional theory calculation reveals that the high-energy surface favors the adsorption of hydrogen intermediate, thus accelerating the hydrogen evolution reaction. The epitaxial growth induced by FSW opens a new avenue toward engineering high-performance catalysts. In addition, FSW makes it possible to massively fabricate low-cost catalyst, which is advantageous to industrial application.

Revealing the Dynamics and Roles of Iron Incorporation in Nickel Hydroxide Water Oxidation Catalysts.

The surface of an electrocatalyst undergoes dynamic chemical and structural transformations under electrochemical operating conditions. There is a dynamic exchange of metal cations between the electrocatalyst and electrolyte. Understanding how iron in the electrolyte gets incorporated in the nickel hydroxide electrocatalyst is critical for pinpointing the roles of Fe during water oxidation. Here, we report that iron incorporation and oxygen evolution reaction (OER) are highly coupled, especially at high working potentials. The iron incorporation rate is much higher at OER potentials than that at the OER dormant state (low potentials). At OER potentials, iron incorporation favors electrochemically more reactive edge sites, as visualized by synchrotron X-ray fluorescence microscopy. Using X-ray absorption spectroscopy and density functional theory calculations, we show that Fe incorporation can suppress the oxidation of Ni and enhance the Ni reducibility, leading to improved OER catalytic activity. Our findings provide a holistic approach to understanding and tailoring Fe incorporation dynamics across the electrocatalyst-electrolyte interface, thus controlling catalytic processes.

Data in Brief of: Clinical benefits of moxifloxacin as initial treatment of community-acquired pneumonia: Data from meta-analyses.

Moxifloxacin and levofloxacin are currently recommended as empirical initial treatment options for community-acquired pneumonia (CAP) in China by clinical guidelines and widely used in clinical settings. Several clinical outcomes comparing the efficacy and safety profiles of moxifloxacin versus levofloxacin through a meta-analysis were reported in paper 'Clinical benefits and cost-effectiveness of moxifloxacin as initial treatment for community-acquired pneumonia: a meta-analysis and economic evaluation'. In this dataset, we aimed at investigating more clinical endpoints comparing the efficacy and safety of moxifloxacin and levofloxacin in the treatment of CAP.

Fine regulation of electron transfer in Ag@Co3O4 nanoparticles for boosting the oxygen evolution reaction.

In this study, a core-shell structure (Ag@Co3O4) was constructed to modify the valence state of cobalt cations precisely by continuously adjusting the shell thickness. There exists a volcano relationship between the valence state of Co sites and OER activity, and the lowest overpotential (212 mV@10 mA cm-2) has been obtained.

Valence-State Effect of Iridium Dopant in NiFe(OH)2 Catalyst for Hydrogen Evolution Reaction.

Engineering high-performance electrocatalysts is of great importance for energy conversion and storage. As an efficient strategy, element doping has long been adopted to improve catalytic activity, however, it has not been clarified how the valence state of dopant affects the catalytic mechanism and properties. Herein, it is reported that the valence state of a doping element plays a crucial role in improving catalytic performance. Specifically, in the case of iridium doped nickel-iron layer double hydroxide (NiFe-LDH), trivalent iridium ions (Ir3+ ) can boost hydrogen evolution reaction (HER) more efficiently than tetravalent iridium (Ir4+ ) ions. Ir3+ -doped NiFe-LDH delivers an ultralow overpotential (19 mV @ 10 mA cm-2 ) for HER, which is superior to Ir4+ doped NiFe-LDH (44 mV@10 mA cm-2 ) and even commercial Pt/C catalyst (40 mV@ 10 mA cm-2 ), and reaches the highest level ever reported for NiFe-LDH-based catalysts. Theoretical and experimental analyses reveal that Ir3+ ions donate more electrons to their neighboring O atoms than Ir4+ ions, which facilitates the water dissociation and hydrogen desorption, eventually boosting HER. The same valence-state effect is found for Ru and Pt dopants in NiFe-LDH, implying that chemical valence state should be considered as a common factor in modulating catalytic performance.

Clinical Benefits and Cost-Effectiveness of Moxifloxacin as Initial Treatment for Community-Acquired Pneumonia: A Meta-Analysis and Economic Evaluation.

PURPOSE: Moxifloxacin and levofloxacin are currently recommended as empirical initial treatment options for community-acquired pneumonia (CAP) in China according to guidelines. Most studies that evaluated the efficacy and safety of moxifloxacin and levofloxacin in treating CAP as initial empirical treatment were single-centered trials assessing different clinical end points. In addition, there is limited research investigating moxifloxacin's clinical benefits in the context of health care resource utilization and reimbursement from the payer's perspective in China. Hence, this study was aimed at comparing the clinical efficacy of moxifloxacin and levofloxacin by conducting a meta-analysis and assessing their economic value from the China payer's perspective through a cost-utility analysis model. METHODS: For the meta-analysis, 6 bibliographic databases were searched for relevant publications from January 2000 to August 2020, and studies were assessed for eligibility under predetermined criteria. Meta-analysis was performed by using a random effects model when analyses included >2 trials. For the economic evaluation, a decision-tree model was constructed to investigate the cost-utility of moxifloxacin versus levofloxacin as initial regimens in the treatment of CAP inpatients. Parameter values were derived from meta-analysis, published literature, and clinician survey. The outcome was reported in the form of an incremental cost-effectiveness ratio. One-way sensitivity analysis and probabilistic sensitivity analysis were undertaken to assess the robustness of the model. FINDINGS: Twenty-seven randomized controlled trials were included in the meta-analysis. Results indicated that the clinical response rate at the test-of-cure visit with initial treatment of moxifloxacin was significantly higher than that of levofloxacin (3441 patients; random effects model; I2 = 49%; odds ratio, 3.35; 95% CI, 2.35-4.77; P < 0.001). In terms of the safety profile, total adverse events were not significantly different between the 2 groups (2770 patients; random effects model; I2 = 40%; odds ratio, 0.77; 95% CI, 0.56-1.06; P = 0.11). Output of the cost-utility model showed that under the willingness-to-pay threshold of one-time China gross domestic product per capita, moxifloxacin is dominant over levofloxacin, being less costly and more efficacious (0.002 quality-adjusted life year gained, CNY 844 [US$131] saved in total cost, negative incremental cost-effectiveness ratio). Sensitivity analyses indicated the robustness of the model as moxifloxacin remained dominant when model parameter values fluctuated. IMPLICATIONS: Moxifloxacin is more efficacious than levofloxacin as the initial empirical treatment for CAP. In addition, treatment of CAP with moxifloxacin instead of levofloxacin is expected to be cost-saving from the perspective of payers in China. However, for the cost-utility analysis, in the absence of a national representative database on costs for hospitalization in China, inputs in the cost-utility model could be underestimated or overestimated due to estimating errors applied to both treatment arms.