Dynamic Modulation of Li2O2 Growth in Li-O2 Batteries through Regulating Oxygen Reduction Kinetics with Photo-Assisted Cathodes.

Widely acknowledged that the capacity of Li-O2 batteries (LOBs) should be strongly determined by growth behaviors of the discharge product of lithium peroxide (Li2O2) that follows both coexisting surface and solution pathways. However until now, it remains still challenging to achieve dynamic modulation on Li2O2 morphologies. Herein, the photo-responsive Au nanoparticles (NPs) supported on reduced oxide graphene (Au/rGO) have been utilized as cathode to manipulate oxygen reduction reaction (ORR) kinetics by aid of surface plasmon resonance (SPR) effects. Thus, we can experimentally reveal the importance of matching ORR kinetics with Li+ migration towards battery performance. Moreover, it is found that Li+ concentration polarization caused "sudden death" of LOBs is supposed to be just a form of suspended animation that could timely recover under irradiation. This work provides us an in-depth explanation on the working mechanism of LOBs from a kinetic perspective, offering valuable insights for the future battery design.

Bayesian Optimization-guided Discovery of High-performance Methane Combustion Catalysts based on Multi-component PtPd@CeZrOx Core-Shell Nanospheres.

Formula regulation of multi-component catalysts by manual search is undoubtedly a time-consuming task, which has severely impeded the development efficiency of high-performance catalysts. In this work, PtPd@CeZrOx core-shell nanospheres, as a successful case study, is explicitly demonstrated how Bayesian optimization (BO) accelerates the discovery of methane combustion catalysts with the optimal formula ratio (the Pt/Pd mole ratio ranges from 1/2.33-1/9.09, and Ce/Zr from 1/0.22-1/0.35), which directly results in a lower conversion temperature (T50 approaching to 330 °C) than ones reported hitherto. Consequently, the best sample obtained could be efficiently developed after two rounds of iterations, containing only 18 experiments in all that is far less than the common human workload via the traditional trial-and-error search for optimal compositions. Further, this BO-based machine learning strategy can be straightforward extended to serve the autonomous discovery in multi-component material systems, for other desired properties, showing promising opportunities to practical applications in future.

Highly Active PdO/Mn3 O4 /CeO2 Nanocomposites Supported on One Dimensional Halloysite Nanotubes for Photoassisted Thermal Catalytic Methane Combustion.

In this work, we have successfully triggered the aqueous auto-redox reactions between reductive Ce(OH)3 and oxidative MnO4 - /Pd2+ ions to form PdO/Mn3 O4 /CeO2 (PMC) nanocomposites. PMC could spontaneously self-assemble into compact encapsulation on the surface of halloysite nanotubes (HNTs) to form the final one dimensional HNTs supported PMCs (HPMC). It is identified that there exists strong synergistic effects among the components of PdO, Mn3 O4 , and CeO2 , and hence HPMC could show excellent performance on photoassisted thermal catalytic CH4 combustion that its light-off temperature was sharply reduced to be 180 °C under visible light irradiation. Based on detailed studies, it is found that the catalytic reaction process well follows the classic MVK mechanism, and adsorption/activation of O2 into active oxygen species (O*) should be the rate-determining step for CH4 conversion.

Solvation Effect on the Improved Sodium Storage Performance of N-Heteropentacenequinone for Sodium-Ion Batteries.

The performance of electrode material is correlated with the choice of electrolyte, however, how the solvation has significant impact on electrochemical behavior is underdeveloped. Herein, N-heteropentacenequinone (TAPQ) is investigated to reveal the solvation effect on the performance of sodium-ion batteries in different electrolyte environment. TAPQ cycled in diglyme-based electrolyte exhibits superior electrochemical performance, but experiences a rapid capacity fading in carbonate-based electrolyte. The function of solvation effect is mainly embodied in two aspects: one is the stabilization of anion intermediate via the compatibility of electrode and electrolyte, the other is the interfacial electrochemical characteristics influenced by solvation sheath structure. By revealing the failure mechanism, this work presents an avenue for better understanding electrochemical behavior and enhancing performance from the angle of solvation effect.

Transition-Metal-Boron Intermetallics with Strong Interatomic d-sp Orbital Hybridization for High-Performance Electrocatalysis.

A theoretical and experimental study gives insights into the nature of the metal-boron electronic interaction in boron-bearing intermetallics and its effects on surface hydrogen adsorption and hydrogen-evolving catalytic activity. Strong hybridization between the d orbitals of transition metal (TM ) and the sp orbitals of boron exists in a family of fifteen TM -boron intermatallics (TM :B=1:1), and hydrogen atoms adsorb more weakly to the metal-terminated intermetallic surfaces than to the corresponding pure metal surfaces. This modulation of electronic structure makes several intermetallics (e.g., PdB, RuB, ReB) prospective, efficient hydrogen-evolving materials with catalytic activity close to Pt. A general reaction pathway towards the synthesis of such TM B intermetallics is provided; a class of seven phase-pure TM B intermetallics, containing V, Nb, Ta, Cr, Mo, W, and Ru, are thus synthesized. RuB is a high-performing, non-platinum electrocatalyst for the hydrogen evolution reaction.

Protecting the Lithium Metal Anode for a Safe Flexible Lithium-Air Battery in Ambient Air.

The flexible Li-air battery (FLAB) with ultrahigh energy density is a hopeful candidate for flexible energy storage devices. However, most current FLAB operate in a pure oxygen atmosphere, which is limited by safety and corrosion issues from the metallic lithium anode and has thus greatly impeded the application of FLAB. Now, inspired by the protection effect of the umbrella, a stable hydrophobic composite polymer electrolyte (SHCPE) film with high flexibility, hydrophobicity, and stability was fabricated to protect the lithium anode. The SHCPE mitigated lithium corrosion and improved the capacity, rate performance, and cycle life (from 24 cycles to 95 cycles) of a battery in the ambient air. Based on the protection of SHCPE and the catalysis of MnOOH, the prepared pouch-type FLAB displayed high flexibility, stable performances, long cycling life (180 cycles), and excellent safety; the battery can bear soaking in water, high temperature, and nail penetration.

An Illumination-Assisted Flexible Self-Powered Energy System Based on a Li-O2 Battery.

The flexible Li-O2 battery is suitable to satisfy the requirements of a self-powered energy system, thanks to environmental friendliness, low cost, and high theoretical energy density. Herein, a flexible porous bifunctional electrode with both electrocatalytic and photocatalytic activity was synthesized and introduced as a cathode to assemble a high-performance Li-O2 battery that achieved an overpotential of 0.19 V by charging with the aid of solar energy. As a proof-of-concept application, a flexible Li-O2 battery was constructed and integrated with a solar cell via a scalable encapsulate method to fabricate a flexible self-powered energy system with excellent flexibility and mechanical stability. Moreover, by exploring the evolution of the electrode morphology and discharge products (Li2 O2 ), the charging process of the Li-O2 battery powered by solar energy and solar cell was demonstrated.

Self-Assembled Pd@CeO2 /γ-Al2 O3 Catalysts with Enhanced Activity for Catalytic Methane Combustion.

Pd@CeO2 /Al2 O3 catalysts are of great importance for real applications, such as three-way catalysis, CO oxidation, and methane combustion. In this article, the Pd@CeO2 core@shell nanospheres are prepared via the autoredox reaction in aqueous phase. Three kinds of methods are then employed, that is, electrostatic interaction, supramolecular self-assembly, and physical mixing, to support the as-prepared Pd@CeO2 nanospheres on γ-Al2 O3 . A model reaction of catalytic methane-combustion is employed here to evaluate the three Pd@CeO2 /γ-Al2 O3 samples. As a result, the sample Pd@CeO2 -S-850 prepared via supramolecular self-assembly and calcined at 850 °C exhibits superior catalytic performance to the others, which has a far lower light-off temperature (T50 of about 364 °C). Moreover, almost no deterioration of Pd@CeO2 -S-850 is observed after five sequent catalytic cycles. The analysis of H2 -TPR curves concludes that there exists hydrogen spillover related to the strong metal-support interaction between Pd species and oxides. The strong metal-support interaction and the specific surface areas might be responsible for the catalytic performance of the Pd@CeO2 samples toward catalytic methane combustion.

Detection of organophosphorous pesticides in soil samples with multiwalled carbon nanotubes coating SPME fiber.

A headspace solid phase microextraction (HS-SPME) technique using stainless steel fiber coated with 20 µm multi-walled carbon nanotubes (MWCNTs) and gas chromatography with thermionic specific detector (GC-TSD) was developed to determine organophosphorous pesticides (OPPs) in soil. Parameters affecting the extraction efficiency such as extraction time and temperature, ionic strength, the volume of water added to the soil, sample solution volume to headspace volume ratio, desorption time, and desorption temperature were investigated and optimized. Compared to commercial polydimethylsiloxane (PDMS, 7 µm) fiber, the PDMS fiber was better to be corrected as phorate, whereas the MWCNTs fiber gave slightly better results for methyl parathion, chlorpyrifos and parathion. The optimized SPME method was applied to analyze OPPs in spiked soil samples. The limits of detection (LODs, S/N = 3) for the four pesticides were <0.216 ng g(-1), and their calibration curves were all linear (r (2) ≥ 0.9908) in the range from 1 to 200 ng g(-1). The precision (RSD, n = 6) for peak areas was 6.5 %-8.8 %. The recovery of the OPPs spiked real soil samples at 50 and 150 ng g(-1) ranged from 89.7 % to 102.9 % and 94.3 % to 118.1 %, respectively.

In Situ Fabrication of Porous Cox P Hierarchical Nanostructures on Carbon Fiber Cloth with Exceptional Performance for Sodium Storage.

Superior high-rate performance and ultralong cycling life have been constantly pursued for rechargeable sodium-ion batteries (SIBs). In this work, a facile strategy is employed to successfully synthesize porous Cox P hierarchical nanostructures supported on a flexible carbon fiber cloth (Cox P@CFC), constructing a robust architecture of ordered nanoarrays. Via such a unique design, porous and bare structures can thoroughly expose the electroactive surfaces to the electrolyte, which is favorable for ultrafast sodium-ion storage. In addition, the CFC provides an interconnected 3D conductive network to ensure firm electrical connection of the electrode materials. Besides the inherent flexibility of the CFC, the integration of the hierarchical structures of Cox P with the CFC, as well as the strong synergistic effect between them, effectively help to buffer the mechanical stress caused by repeated sodiation/desodiation, thereby guaranteeing the structural integrity of the overall electrode. Consequently, Cox P@CFC as an anode shows a record-high capacity of 279 mAh g-1 at 5.0 A g-1 with almost no capacity attenuation after 9000 cycles.

3D Carbon Networks: Design and Applications in Sodium Ion Batteries.

As the key component of a new generation for low-cost energy storage systems, sodium-ion batteries (SIBs) have attracted enormous attention and research due to its promising potentiality in large-scale electrochemical energy storage. For practical application of SIBs, carbonaceous materials have been considered to be one of the best choices for electrodes in virtue of their abundant reserves, low cost, easy availability, and environmental friendliness. 3D carbon network (3D-carbon) is of particular interests, which has displayed outstanding features, including abundant active sites, interconnected multi-level pore structures, high electronic conductivity, and excellent mechanical stability. Herein, we review the structural advantages of 3D-carbon and its preparation methods, and then discuss recent progress in 3D carbon materials and their composites for SIBs. The superior functionalities of 3D-carbon are emphasized as support templates or encapsulation shell membranes. Finally, we summarize and outline the challenges and future prospects of 3D-carbon in SIBs.

Layer-by-Layer Electrodeposition of FTO/TiO2 /Cux O/CeO2 (1 < x < 2) Photocatalysts with High Peroxidase-Like Activity by Greatly Enhanced Singlet Oxygen Generation.

Inorganic nanomaterials have attracted much attention as enzyme mimics because of simple and stable spatial conformation of those artificially synthesized nanocatalysts. Cu2 O, as an important kind of narrow band gap semiconductor, is identified as effective as visible-light-driven photocatalysts, which can catalyze decomposition of H2 O2 into reactive oxygen species. Moreover, after forming Cux O/CeO2 hybrids, the strongly coupled interface between the two components will further improve their catalytic performance. In this paper, the authors try to construct FTO/TiO2 /Cux O/CeO2 (1 < x < 2) nanohybrids with such a kind of active interface via a layer-by-layer electrodeposition strategy by aid of the following surface etching process. It is found that FTO/TiO2 /Cux O/CeO2 exhibits good peroxidase mimic activity in the dark but much better performance under visible light irradiation (λ ≥ 420 nm) during catalytic oxidation of 3,3',5,5'-tetramethylbenzidine substrates in the presence of H2 O2 . Detailed characterizations disclose that the construction of TiO2 /Cu2 O pn-heterojunctions do effectively accelerate separation of photogenerated carriers, and the formation of a highly active Cux O/CeO2 interface is synergistically favorable for selectively generating singlet oxygen to boost the catalytic performance of FTO/TiO2 /Cux O/CeO2 .

Determination of Volatile Water Pollutants Using Cross-Linked Polymeric Ionic Liquid as Solid Phase Micro-Extraction Coatings.

Ionic liquids found a wide application in catalysis and extraction due to their unique properties. Herein, ethylene glycol dimethacrylate as the cross-linker and 1-vinyl-3- butylimidazolium tetrafluoroborate as functional monomer via thermally initiated free-radical polymerization was prepared as a novel copolymer solid phase micro-extraction (SPME) coating. A surface modified stainless-steel wire was implemented as the substrate. Factors affecting the extraction performances of the copolymer, including the molar ratio of monomers to cross-linkers, the amount of porogen agent, and polymerization time were evaluated and optimized. To evaluate the extraction performance, five commonly seen polycyclic aromatic hydrocarbons (PAHs) were taken as the analytical targets. The potential factors affecting extraction efficiency were optimized. The as-prepared SPME device, coupled with gas chromatography, was successfully applied for the determination of PAHs in water samples. The wide linear range, low detection limit, good reproducibility, selectivity, and excellent thermal stability indicate the promising application of the newly developed SPME fiber in environmental monitoring as well as in other samples having complex matrices.

Flexible Electrodes for Sodium-Ion Batteries: Recent Progress and Perspectives.

Sodium-ion batteries (SIBs) are considered as promising alternatives to lithium-ion batteries (LIBs) for large-scale electrical-energy-storage applications due to the wide availability and the low cost of Na resources. Along with the avenues of research on flexible LIBs, flexible SIBs are now being actively developed as one of the most promising power sources for the emerging field of flexible and wearable electronic devices. Here, the recent progress on flexible electrodes based on metal substrates, carbonaceous substrates (i.e., graphene, carbon cloth, and carbon nanofibers), and other materials, as well as their applications in flexible SIBs, are summarized. Also, some future research directions for constructing flexible SIBs are proposed, with the aim of providing inspiration to the further development of advanced flexible SIBs.

Decoration of Pt on Cu/Co double-doped CeO2 nanospheres and their greatly enhanced catalytic activity.

In this paper, we report an efficient strategy for the synthesis of Cu/Co double-doped CeO2 nanospheres (Cu x Co1-x -CeO2-Pt, 0 ≤ x ≤ 1), which were fabricated via a simple water-glycol system. The following in situ surface decoration of Pt nanoparticles make these nanospheres highly active for the catalytic reduction of nitrophenol and CO oxidation. Detailed tests show that their catalytic performance strongly depends on the doping components and ion concentration of Cu and Co ions. The best samples of Cu0.50Co0.50-CeO2-Pt and Cu0.34Co0.66-CeO2-Pt demonstrate an excellent turnover frequency (TOF) of more than 450 h-1 after five cycles and retains about 99% conversion by using NH3BH3 as a reductant to reduce nitrophenol. Moreover, Cu0.50Co0.50-CeO2-Pt possesses a much lower light-off and T100 (the temperature for 100% CO oxidation) temperature compared with the other catalysts.

Galvanic replacement synthesis of Ag x Au1-x @CeO2 (0 ≤ x ≤ 1) core@shell nanospheres with greatly enhanced catalytic performance.

A galvanic replacement strategy has been successfully adopted to design Ag x Au1-x @CeO2 core@shell nanospheres derived from Ag@CeO2 ones. After etching using HAuCl4, the Ag core was in situ replaced with Ag x Au1-x alloy nanoframes, and void spaces were left under the CeO2 shell. Among the as-prepared Ag x Au1-x @CeO2 catalysts, Ag0.64Au0.36@CeO2 shows the optimal catalytic performance, whose catalytic efficiency reaches even 2.5 times higher than our previously reported Pt@CeO2 nanospheres in the catalytic reduction of 4-nitrophenol (4-NP) by ammonia borane (AB). Besides, Ag0.64Au0.36@CeO2 also exhibits a much lower 100% conversion temperature of 120 °C for catalytic CO oxidation compared with the other samples.