A facile coprecipitation approach for synthesizing LaNi0.5Co0.5O3 as the cathode for a molten-salt lithium-oxygen battery.

The cathode of a lithium-oxygen battery (LOB) should be well designed to deliver high catalytic activity and long stability, and to provide sufficient space for accommodating the discharge product. Herein, a facile coprecipitation approach is employed to synthesize LaNi0.5Co0.5O3 (LNCO) perovskite oxide with a low annealing temperature. The assembled LOB exhibits superior electrochemical performance with a low charge overpotential of 0.03-0.05 V in the current density range of 0.1-0.5 mA cm-2. The battery ran stably for 119 cycles at a high coulombic efficiency. The superior performance is ascribed to (i) the high catalytic activity of LNCO towards oxygen reduction/evolution reactions; (ii) the increased temperature enabling fast kinetics; and (iii) the LiNO3-KNO3 molten salt enhancing the stability of the LOB operating at high temperature.

Engineering the NASICON electrolyte/Na anode interface with amorphous bismuth oxide for sodium batteries.

Amorphous BiOx, prepared on the surface of NASICON electrolyte by the photochemical metal-organic deposition method, can substantially improve the interfacial properties at the anode side. The Na symmetric cell delivers a critical current density of 1.2 mA cm-2 and cycles stably at 0.5 mA cm-2 for 1000 h at 30 °C.

Photoelectrocatalytic treatment of municipal wastewater with emerging concern pollutants using modified multi-layer catalytic anode.

Municipal wastewater contains emergent chemical and biological pollutants that are resistant to conventional wastewater treatments. Therefore, the focus of the current study was to address the challenge of removing emergent chemical and biological pollutants present in municipal wastewater. To achieve this, a photo electro-catalytic (PEC) treatment approach was employed, focusing on the removal of both micro and biological pollutants that are of emergent concern, as well as the reduction of Chemical Oxidation Demand (COD) and Total Organic Carbon (TOC). The treatment involved the use of a modified multi-layer catalytic anode photo-electroactive anode as an effective anode for PEC treatment of municipal wastewater. In the continuous mode of operation, %COD removal was optimized for the treatment of municipal wastewater under Ultra-Violet C (UVc), 280 nm, and Visible (Vis) radiation, 400 nm. Therefore, a comparative study was performed to investigate the effect of Vis radiation on %COD removal, micropollutants removal, and disinfection of municipal wastewater. Micropollutants present in municipal wastewater were effectively oxidized/degraded with the highest reduction rate between 100% and 80% under the influence of UVc and Vis radiation respectively by the PEC treatment process. Disinfection of various microorganisms present in the wastewater with the effect of UVc and Vis assisted PEC treatment was also monitored. Overall, 75-80% of the disinfection of municipal wastewater was contributed by the modified multi-layer catalytic anode. The UVc in the PEC system, contributes approximately 20-25% to the overall disinfection of municipal wastewater.

A metal-free carbon catalyst for oxidative dehydrogenation of aryl cyclohexenes to produce biaryl compounds.

A metal-free route based on a carbon catalyst to synthesize biphenyls through oxidative dehydrogenation (ODH) of phenyl cyclohexene has been investigated. Among the samples examined, an air-oxidized active carbon exhibits the best activity with a 9.1 × 10-2 h-1 rate constant, yielding 74% biphenyl in 28 h at 140 °C under five bar O2 in anisole. The apparent activation energy is measured as 54.5 kJ⋅mol-1. The extended reaction scope, consisting of 15 differently substituted phenyl cyclohexenes, shows the wide applicability of the proposed method. The catalyst's good recyclability over six runs suggests this ODH method as a promising route to access the biaryl compounds. In addition, the reaction mechanism is investigated with a combination of X-ray photoelectron spectroscopy, functional group blocking, and model compounds of carbon catalysts and is proposed to be based on the redox cycle of the quinoidic groups on the carbon surface. Additional experiments prove that the addition of the catalytic amount of acid (methanesulfonic acid) accelerates the reaction. In addition, Hammett plot examination suggests the formation of a carbonium intermediate, and its possible structure is outlined.

Recent Progress in the Integration of CO2 Capture and Utilization.

CO2 emission is deemed to be mainly responsible for global warming. To reduce CO2 emissions into the atmosphere and to use it as a carbon source, CO2 capture and its conversion into valuable chemicals is greatly desirable. To reduce the transportation cost, the integration of the capture and utilization processes is a feasible option. Here, the recent progress in the integration of CO2 capture and conversion is reviewed. The absorption, adsorption, and electrochemical separation capture processes integrated with several utilization processes, such as CO2 hydrogenation, reverse water-gas shift reaction, or dry methane reforming, is discussed in detail. The integration of capture and conversion over dual functional materials is also discussed. This review is aimed to encourage more efforts devoted to the integration of CO2 capture and utilization, and thus contribute to carbon neutrality around the world.

Fast and Durable Lithium Storage Enabled by Tuning Entropy in Wadsley-Roth Phase Titanium Niobium Oxides.

Wadsley-Roth phase titanium niobium oxides have received considerable interest as anodes for lithium ion batteries. However, the volume expansion and sluggish ion/electron transport kinetics retard its application in grid scale. Here, fast and durable lithium storage in entropy-stabilized Fe0.4 Ti1.6 Nb10 O28.8 (FTNO) is enabled by tuning entropy via Fe substitution. By increasing the entropy, a reduction of the calcination temperature to form a phase pure material is achieved, leading to a reduced grain size and, therefore, a shortening of Li+ pathway along the diffusion channels. Furthermore, in situ X-ray diffraction reveals that the increased entropy leads to the decreased expansion along a-axis, which stabilizes the lithium intercalation channel. Density functional theory modeling indicates the origin to be the more stable FeO bond as compared to TiO bond. As a result, the rate performance is significantly enhanced exhibiting a reversible capacity of 73.7 mAh g-1 at 50 C for FTNO as compared to 37.9 mAh g-1 for its TNO counterpart. Besides, durable cycling is achieved by FTNO, which delivers a discharge capacity of 130.0 mAh g-1 after 6000 cycles at 10 C. Finally, the potential impact for practical application of FTNO anodes has been demonstrated by successfully constructing fast charging and stable LiFePO4 ‖FTNO full cells.

Cold-Start NOx Mitigation by Passive Adsorption Using Pd-Exchanged Zeolites: From Material Design to Mechanism Understanding and System Integration.

It remains a major challenge to abate efficiently the harmful nitrogen oxides (NOx) in low-temperature diesel exhausts emitted during the cold-start period of engine operation. Passive NOx adsorbers (PNA), which could temporarily capture NOx at low temperatures (below 200 °C) and release the stored NOx at higher temperatures (normally 250-450 °C) to downstream selective catalytic reduction unit for complete abatement, hold promise to mitigate cold-start NOx emissions. In this review, recent advances in material design, mechanism understanding, and system integration are summarized for PNA based on palladium-exchanged zeolites. First, we discuss the choices of parent zeolite, Pd precursor, and synthetic method for the synthesis of Pd-zeolites with atomic Pd dispersions, and review the effect of hydrothermal aging on the properties and PNA performance of Pd-zeolites. Then, we show how different experimental and theoretical methodologies can be integrated to gain mechanistic insights into the nature of Pd active sites, the NOx storage/release chemistry, as well as the interactions between Pd and typical components/poisons in engine exhausts. This review also gathers several novel designs of PNA integration into modern exhaust after-treatment systems for practical application. At the end, we discuss the major challenges, as well as important implications, for the further development and real application of Pd-zeolite-based PNA in cold-start NOx mitigation.

Solid oxide fuel cell with a spin-coated yttria stabilized zirconia/gadolinia doped ceria bi-layer electrolyte.

A thin yttria stabilized zirconia (YSZ)/gadolinia doped ceria (GDC) bi-layer membrane is fabricated through the slurry spin coating technique and used as an electrolyte of a solid oxide fuel cell with La0.6Sr0.4Co0.2Fe0.8O3-δ as the cathode. The viscosity of the YSZ slurry is controlled by adding ethanol in the terpineol solvent, which shows a negligible effect on the thickness but a remarkable influence on the porosity of the YSZ film. The thickness of the YSZ layer increases with the YSZ content in the slurry. The YSZ films are pre-sintered at various temperatures, and the one sintered at 1200 °C has a moderate interaction with the GDC slurry, forming a 10 µm-thick YSZ/GDC bilayer with a low porosity and a low ohmic resistance. The corresponding single cell shows a maximum power density of 1480 mW cm-2 at 750 °C.

Coupling Tetraalkylammonium and Ethylene Glycol Ether Side Chain To Enable Highly Soluble Anthraquinone-Based Ionic Species for Nonaqueous Redox Flow Battery.

Nonaqueous redox flow batteries (NARFBs) have promise for large-scale energy storage with high energy density. Developing advanced active materials is of paramount importance to achieve high stability and energy density. Herein, we adopt the molecular engineering strategy by coupling tetraalkylammonium and an ethylene glycol ether side chain to design anthraquinone-based ionic active species. By adjusting the length of the ethylene glycol ether chain, an ionic active species 2-((9,10-dioxo-9,10-dihydroanthracen-1-yl)amino)-N-(2-(2-methoxyethoxy)ethyl)-(N,N-dimethylethan-1-aminium)-bis(trifluoromethylsulfonyl)imide (AQEG2TFSI) with high solubility and stability is obtained. Paired with a FcNTFSI cathode, the full battery provides an impressive cycling performance with discharge capacity retentions of 99.96% and 99.74% per cycle over 100 cycles with 0.1 and 0.4 M AQEG2TFSI, respectively.

Liquid Nitrobenzene-Based Anolyte Materials for High-Current and -Energy-Density Nonaqueous Redox Flow Batteries.

Nonaqueous redox flow batteries (NARFBs) are a potential candidate for high-energy-density storage systems because of their wider electrochemical windows than that of the aqueous systems. However, their further development is hindered by the low solubility of organic redox-active materials and poor high-current operations. Herein, we report a liquid anolyte material, 3-nitrotoluene (3-NT), which demonstrates high chemical stability and mass- and charge-transfer kinetics. The NARFB based on 2,5-di-tert-butyl-1-methoxy-4-[2'-methoxyethoxy]benzene/3-NT exhibits an energy efficiency of 71.8% even at a relatively high current density of 60 mA cm-2. Benefiting from the high miscibility of the redox species, an ultra-high volumetric energy density of 37.8 W h L-1 can be achieved at 1.0 M. This work provides a viable method to build an NARFB with both high operational current density and energy density for next-generation, low-cost, and high-energy storage systems.

Catalytic conversion of enzymatic hydrolysis lignin into cycloalkanes over a gamma-alumina supported nickel molybdenum alloy catalyst.

The efficient depolymerization and hydrodeoxygenation of enzymatic hydrolysis lignin are achieved in cyclohexane solvents over a gamma-alumina supported nickel molybdenum alloy catalyst in a single step. Under initial 3 MPa hydrogen at 320 °C, the highest overall cycloalkane yield of 104.4 mg/g enzymatic hydrolysis lignin with 44.4 wt% selectivity of ethyl-cyclohexane was obtained. The reaction atmosphere and temperature have significant effects on enzymatic hydrolysis lignin conversion, product type and distribution. The conversion of enzymatic hydrolysis lignin was also investigated over different nickel and molybdenum-based catalysts, and the gamma-alumina supported nickel molybdenum alloy catalyst exhibited the highest activity among those catalysts. To reveal the reaction pathways of alkylphenol hydrodeoxygenation, 4-ethylphenol was tested as a model compound. Complete conversion of 4-ethylphenol into cycloalkanes was achieved. A two-step mechanism of 4-ethylphenol dihydroxylation - hydrogenation is proposed, in which the benzene ring saturation is deemed as the rate-determining step.

A-Site Ordered Double Perovskite with in Situ Exsolved Core-Shell Nanoparticles as Anode for Solid Oxide Fuel Cells.

A highly active anode material for solid oxide fuel cells resistant to carbon deposition is developed. Co-Fe co-doped La0.5Ba0.5MnO3-δ with a cubic-hexagonal heterogeneous stucture is synthesized through the Pechini method. An A-site ordered double perovskite with Co0.94Fe0.06 alloy-oxide core-shell nanoparticles on its surface is formed after reduction. The phase transition and the exsolution of the nanoparticles are investigated with X-ray diffraction, thermogravimetric analysis, and high-resolution transmission electron microscope. The exsolved nanoparticles with the layered double-perovskite supporter show a high catalytic activity. A single cell with that anode and a 300 µm thick La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte layer exhibits maximum power densities of 1479 and 503 mW cm-2 at 850 °C with wet hydrogen and wet methane fuels, respectively. Moreover, the single cell fed with wet methane exhibits a stable power output at 850 °C for 200 h, demonstrating a high resistance to carbon deposition of the anode due to the strong anchor of the exsolved nanoparticles on the perovskite parent. The oxide shell also preserves the metal particles from coking.

Highly selective conversion of guaiacol to tert-butylphenols in supercritical ethanol over a H2WO4 catalyst.

The conversion of guaiacol is examined at 300 °C in supercritical ethanol over a H2WO4 catalyst. Guaiacol is consumed completely, meanwhile, 16.7% aromatic ethers and 80.0% alkylphenols are obtained. Interestingly, tert-butylphenols are produced mainly with a high selectivity of 71.8%, and the overall selectivity of 2,6-di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol is as high as 63.7%. The experimental results indicate that catechol and 2-ethoxyphenol are the intermediates. Meanwhile, the WO3 sites play an important role in the conversion of guaiacol and the Brønsted acid sites on H2WO4 enhance the conversion and favour a high selectivity of the tert-butylphenols. The recycling tests show that the carbon deposition on the catalyst surface, the dehydration and partial reduction of the catalyst itself are responsible for the decay of the H2WO4 catalyst. Finally, the possible reaction pathways proposed involve the transetherification process and the alkylation process during guaiacol conversion.

An all organic redox flow battery with high cell voltage.

An all organic redox flow battery with 4,4'-dimethylbenzophenone (44DMBP) anolyte and 2,5-di-tert-butyl-1,4-dimethoxybenzene (DBB) catholyte shows a high open circuit voltage of 2.97 V, and average coulombic efficiency of 72% over 95 cycles at a current density of 1 mA cm-2.

Facile Preparation of Haggite by Reducing V2O5 in Guaiacol/Methanol Solution.

Haggite-structured V4O6(OH)4 is prepared via a one-step reduction of V2O5 in a mixture of guaiacol and methanol. Guaiacol delays the overreduction of Haggite to V2O3. The time window for the stable existence of the Haggite phase is enlarged at low temperature.

A systematic study of the co-solvent effect for an all-organic redox flow battery.

Benzophenone and 1,4-di-tert-butyl-2,5-dimethoxybenzene are used as the anode and cathode active species respectively in an all-organic redox-flow battery. A number of organics as the co-solvents are applied in the electrolyte to improve the electrochemical performance of it. For all kinds of the mixed solvents, a lower content of acetonitrile leads to a higher solubility to 1,4-di-tert-butyl-2,5-dimethoxybenzene and a lower conductivity. The results of cyclic voltammetry tests demonstrate that the electrode reactions are controlled by diffusion. With the decrease of the content of acetonitrile, the dynamic viscosity of the electrolyte increases, which generally leads to the decrease of the diffusion coefficients of the active species.

Near- and supercritical ethanol treatment of biocrude from hydrothermal liquefaction of microalgae.

Biocrude produced from algae by hydrothermal liquefaction was treated with near- and supercritical ethanol and ethanol-water mixtures at 210-290°C for 0.5-4h. Longer reaction times and higher temperatures better promoted esterification reactions. Dilution of the ethanol with water led to lower yields of treated biocrude and reduced ester content. The viscosity of treated biocrude was an order of magnitude lower than that of the crude bio-oil, and the treated biocrude exhibited the characteristics of a Newtonian fluid. Overall, treatment of biocrude with near- and supercritical ethanol generated a treated bio-oil with lower viscosity, more ester content, and in nearly 100wt% yield.

Catalytic conversion of Chlorella pyrenoidosa to biofuels in supercritical alcohols over zeolites.

Microalgae have been considered as the feedstock for the third generation biofuels production, given its high lipid content and fast productivity. Herein, a catalytic approach for microalgae liquefaction to biocrude is examined in a temperature range of 250-300°C in methanol and ethanol over zeolites. Higher biocrude yield was achieved in ethanol and at lower temperatures, while better quality biocrude with higher light biocrude ratio and lower average molecular weight (Mw) was favored in methanol and at higher temperatures. Application of zeolites improves the biocrude quality significantly. Among the catalysts, HY shows the strongest acidity and performs the best to produce high quality biocrude. Solid residues have been extensively explored with thermal gravity analysis and elemental analysis. It is reported for the first time that up to 99wt.% of sulfur is deposited in the solid residue at 250°C for both solvents.

Facet-selective charge carrier transport, deactivation mechanism and stabilization of a Cu2O photo-electro-catalyst.

A facet-dependent photo-deactivation mechanism of Cu2O was verified and reported, which is caused by the facet-dependent charge carrier transport. During irradiation, the {100} and {110} crystal facets are selectively corroded by the photo-generated holes, while the {111} facets are comparatively stable.

Templating Sol-Gel Hematite Films with Sacrificial Copper Oxide: Enhancing Photoanode Performance with Nanostructure and Oxygen Vacancies.

Nanostructuring hematite films is a critical step for enhancing photoelectrochemical performance by circumventing the intrinsic limitations on minority carrier transport. Herein, we present a novel sol-gel approach that affords nanostructured hematite films by including CuO as sacrificial templating agent. First, by annealing in air at 450 °C a film comprising an intimate mixture of CuO and Fe2O3 nanoparticles is obtained. The subsequent treatment with NaCl and annealing at 700 °C under Argon reveals a nanostructured highly crystalline hematite film devoid of copper. Photoelectrochemical investigations reveal that the incorporation of CuO as templating agent and the inert conditions employed during the annealing play a crucial role in the performance of the hematite electrodes. Mott-Schottky analysis shows a higher donor concentration when annealing in inert conditions, and even higher when combined with the NaCl treatment. These findings agree well with the presence of an oxygen-deficient shell on the material's surface evidenced by FT-IR and XPS measurements. Likewise, the incorporation of the CuO enhances the photocurrent obtained at 1.23 V from 0.55 to 0.8 mA·cm(-2) because of an improved nanostructure. Optimized films demonstrate an incident photon-to-current efficiency (IPCE) of 52% at 380 nm when applying 1.23 V versus RHE, and a faradaic efficiency for water splitting close to unity.