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Abstract: Oxygen evolution reaction (OER) in acid media has been intensively studied recently for its important role in proton exchange membrane electrolyzers. CeO2-based nanomaterials have been widely used in various applications for their redox properties, oxygen vacancy, and surface activity. CeO2-based nanocatalysts also exhibit superior catalytic performance in OER in acid media. Herein, we fabricated a highly efficient catalytic interface between IrOx and CeO2 (IrOx/CeO2), which showed a boosting OER activity with an overpotential of 217 mV at the current density of 10 mA/cm2 and long-term stability for 10 h in 0.5 mol/L H2SO4, which were better than those of many reported catalysts. The in situ differential electrochemical mass spectrometry results demonstrated that IrOx/CeO2 and the commercial IrO2 (IrO2-com) followed the adsorbate evolution mechanism, whereas the pure CeO2 surface followed the lattice oxygen oxidation mechanism under the same conditions for OER. These indicated that the interface of IrOx and CeO2 improved mass transfer efficiency and reactivity, which also prevented the lattice oxygen evolution in the CeO2 structure and protected the whole structure. This work finds a new way for OER in acid media catalyzed by CeO2-based nanocatalysts and promotes the design strategy for other CeO2-based nanostructures. Graphical PubDate: 2023-11-28
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Abstract: Abstract Reversible protonic ceramic electrochemical cells (R-PCECs) are ideal, high-efficiency devices that are environmentally friendly and have a modular design. This paper studies BaFe0.6Zr0.1Y0.3O3−δ (BFZY3) as a cobalt-free perovskite oxygen electrode for high-performance R-PCECs where Y ions doping can increase the concentration of oxygen vacancies with a remarkable increase in catalytic performance. The cell with configuration of Ni-BZCYYb/BZCYYb/BFZY3 demonstrated promising performance in dual modes of fuel cells (FCs) and electrolysis cells (ECs) at 650 °C with low polarization resistance of 0.13 Ω cm2, peak power density of 546.59 mW/cm2 in FC mode, and current density of − 1.03 A/cm2 at 1.3 V in EC mode. The alternative operation between FC and EC modes for up to eight cycles with a total of 80 h suggests that the cell with BFZY3 is exceptionally stable and reversible over the long term. The results indicated that BFZY3 has considerable potential as an air electrode material for R-PCECs, permitting efficient oxygen reduction and water splitting. PubDate: 2023-11-27
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Abstract: Abstract Developing nonprecious metal-nitrogen-doped carbon (M–N–C) catalysts with high activity and stability is critical to their widespread use in fuel cells; however, these catalysts still face considerable challenges. Herein, a novel iron atom-cluster strategy for the synthesis of iron-based N–C catalyst comprising Fe nanoparticles (Fe NPs) surrounded by Fe-Nx sites is developed for oxygen reduction reactions in an acidic fuel cell. Iron oxide NPs were incorporated into zeolitic imidazolate framework-8 (ZIF-8)-derived carbon materials and pyrolyzed at high temperatures using NaCl as a modifier to produce Fe NPs and Fe-Nx composite active sites. The half-wave potential of the optimized FeNP/FeNC-NaCl material was substantially improved to 0.81 V. Furthermore, even after 15,000 cycles, the half-wave potential of the catalyst remained essentially unchanged. As a cathode catalyst for fuel cells, it realized a high peak power density of 436 mW/cm2 under a practical H2-air atmosphere. Therefore, this study presents a new approach for designing and synthesizing electrocatalytic materials with high catalytic activity and stability. PubDate: 2023-11-20
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Abstract: Abstract The electrode ionomer plays a crucial role in the catalyst layer (CL) of a proton-exchange membrane fuel cell (PEMFC) and is closely associated with the proton conduction and gas transport properties, structural stability, and water management capability. In this review, we discuss the CL structural characteristics and highlight the latest advancements in ionomer material research. Additionally, we comprehensively introduce the design concepts and exceptional performances of porous electrode ionomers, elaborate on their structural properties and functions within the fuel cell CL, and investigate their effect on the CL microstructure and performance. Finally, we present a prospective evaluation of the developments in the electrode ionomer for fabricating CL, offering valuable insights for designing and synthesizing more efficient electrode ionomer materials. By addressing these facets, this review contributes to a comprehensive understanding of the role and potential of electrode ionomers for enhancing PEMFC performance. PubDate: 2023-11-16
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Abstract: Abstract Zinc-ion batteries (ZIBs) with low cost and high safety have become potential candidates for large-scale energy storage. However, the knotty Zn anode issues such as dendritic growth, hydrogen evolution reaction (HER) and corrosion and passivation are still unavoidable, which greatly limits the wide applications of ZIBs. The states and additives of electrolytes are closely related to these problems. However, there is a lack of systematic understanding and discussion about the intrinsic connection between the states and additives of electrolyte and Zn anode issues. In this review, the basic principles of dendritic growth, HER and corrosion and passivation are firstly introduced, and then, electrolyte optimization strategies with the corresponding electrochemical properties are systematically summarized. In particular, the action mechanism of electrolyte additives and the electrolyte states for Zn anode optimization is analyzed in detail. Finally, some unique views on the improvement of electrolyte for Zn anode optimization are put forward, which is expected to provide a certain professional reference for designing high-performance ZIBs. PubDate: 2023-11-10
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Abstract: Abstract Hydrogenative rearrangement of biomass-derived furfurals (furfural and 5-hydroxymethyl furfural) to C5 cyclic compounds (such as cyclopentanones and cyclopentanols) offers an expedient reaction route for acquiring O-containing value-added chemicals thereby replacing the traditional petroleum-based approaches. The scope for developing efficient bifunctional catalysts and establishing mild reaction conditions for upgrading furfurals to cyclic compounds has stimulated immense deliberation in recent years. Extensive efforts have been made toward developing catalysts for multiple tandem conversions, including those with various metals and supports. In this scientific review, we aim to summarize the research progress on the synergistic effect of the metal–acid sites, including simple metal–supported acidic supports, adjacent metal acid sites–supported catalysts, and in situ H2-modified bifunctional catalysts. Distinctively, the catalytic performance, catalytic mechanism, and future challenges for the hydrogenative rearrangement are elaborated in detail. The methods highlighted in this review promote the development of C5 cyclic compound synthesis and provide insights to regulate bifunctional catalysis for other applications. PubDate: 2023-11-03
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Abstract: Abstract Aqueous rechargeable batteries are safe and environmentally friendly and can be made at a low cost; as such, they are attracting attention in the field of energy storage. However, the temperature sensitivity of aqueous batteries hinders their practical application. The solvent water freezes at low temperatures, and there is a reduction in ionic conductivity, whereas it evaporates rapidly at high temperatures, which causes increased side reactions. This review discusses recent progress in improving the performance of aqueous batteries, mainly with respect to electrolyte engineering and the associated strategies employed to achieve such improvements over a wide temperature domain. The review focuses on five electrolyte engineering (aqueous high-concentration electrolytes, organic electrolytes, quasi-solid/solid electrolytes, hybrid electrolytes, and eutectic electrolytes) and investigates the mechanisms involved in reducing the solidification point and boiling point of the electrolyte and enhancing the extreme-temperature electrochemical performance. Finally, the prospect of further improving the wide temperature range performance of aqueous rechargeable batteries is presented. PubDate: 2023-10-17
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Abstract: Abstract The use of carbonized wood in various functional devices is attracting considerable attention due to its low cost, vertical channels, and high electrical conduction. However, the conventional carbonization method requires a long processing time and an inert atmosphere. Here, a microwave-assisted ultrafast carbonization technique was developed that carbonizes natural wood in seconds without the need for an inert atmosphere, and the obtained aligned-porous carbonized wood provided an excellent electrochemical performance as an anode material for lithium-ion batteries. This ultrafast carbonization technique simultaneously produced ZnO nanoparticles during the carbonization process that were uniformly distributed on the aligned-porous carbon. The hierarchical structure of carbonized wood functionalized with ZnO nanoparticles was used as a host for achieving high-performance lithium–sulfur batteries: the highly conductive carbonized wood framework with vertical channels provided good electron transport pathways, and the homogeneously dispersed ZnO nanoparticles effectively adsorbed lithium polysulfide and catalyzed its conversion reactions. In summary, a new method was developed to realize the ultrafast carbonization of biomass materials with decorated metal oxide nanoparticles. PubDate: 2023-09-01
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Abstract: Abstract Water electrolysis, a process for producing green hydrogen from renewable energy, plays a crucial role in the transition toward a sustainable energy landscape and the realization of the hydrogen economy. Oxygen evolution reaction (OER) is a critical step in water electrolysis and is often limited by its slow kinetics. Two main mechanisms, namely the adsorbate evolution mechanism (AEM) and lattice oxygen oxidation mechanism (LOM), are commonly considered in the context of OER. However, designing efficient catalysts based on either the AEM or the LOM remains a topic of debate, and there is no consensus on whether activity and stability are directly related to a certain mechanism. Considering the above, we discuss the characteristics, advantages, and disadvantages of AEM and LOM. Additionally, we provide insights on leveraging the LOM to develop highly active and stable OER catalysts in future. For instance, it is essential to accurately differentiate between reversible and irreversible lattice oxygen redox reactions to elucidate the LOM. Furthermore, we discuss strategies for effectively activating lattice oxygen to achieve controllable steady-state exchange between lattice oxygen and an electrolyte (OH− or H2O). Additionally, we discuss the use of in situ characterization techniques and theoretical calculations as promising avenues for further elucidating the LOM. PubDate: 2023-08-16
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Abstract: Abstract The lattice oxygen oxidation mechanism (LOM) provides an efficient pathway for accelerating the oxygen evolution reaction (OER) in certain electrocatalysts by activating and involving lattice oxygen in the catalytic OER process. We investigated the potential of disordered rocksalts as catalysts for accelerating the OER through the LOM process, leveraging their unique metastable Li–O–Li bond states. Theoretical calculations were employed to predict the catalytic pathways and activities of disordered rocksalts (DRX), such as Li1.2Co0.4Ti0.5O2 (LCTO). The results revealed that benefiting from the unhybridized Li–O electronic orbitals and the resulting metastable states of Li–O–Li bonds in DRX, LCTO exhibited a typical LOM pathway, and the lattice oxygen was easily activated and participated in the OER. The experimental results showed that LCTO exhibited a remarkable pH-dependent OER activity through the LOM pathway, with an overpotential of 241 mV at a current density of 10 mA/cm2, and excellent long-term stability. This work provides a novel chemical space for designing highly active and stable OER electrocatalysts by leveraging the LOM reaction pathway. PubDate: 2023-08-02
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Abstract: Abstract Vanadium flow batteries (VFBs) are considered ideal for grid-scale, long-duration energy storage applications owing to their decoupled output power and storage capacity, high safety, efficiency, and long cycle life. However, the widespread adoption of VFBs is hindered by the use of expensive Nafion membranes. Herein, we report a soft template-induced method to develop a porous polyvinylidene fluoride (PVDF) membrane for VFB applications. By incorporating water-soluble and flexible polyethylene glycol (PEG 400) as a soft template, we induced the aggregation of hydrophilic sulfonated poly (ether ether ketone), resulting in phase separation from the hydrophobic PVDF polymer during membrane formation. This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution. The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm2, and the VFB exhibited a Coulombic efficiency of 95.2% and a voltage efficiency of 87.8%. These findings provide valuable insights for the development of highly stable membranes for VFB applications. PubDate: 2023-07-25
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Abstract: Abstract Liquid metal gallium has been widely used in numerous fields, from nuclear engineering, catalysts, and energy storage to electronics owing to its remarkable thermal and electrical properties along with low viscosity and nontoxicity. Compared with high-temperature liquid metals, room-temperature liquid metals, such as gallium (Ga), are emerging as promising alternatives for fabricating advanced energy storage devices, such as phase change materials, by harvesting the advantageous properties of their liquid state maintained without external energy input. However, the thermal and electrical properties of liquid metals at the phase transition are rather poorly studied, limiting their practical applications. In this study, we reported on the physical properties of the solid–liquid phase transition of Ga using a custom-designed, solid–liquid electrical and thermal measurement system. We observed that the electrical conductivity of Ga progressively decreases with an increase in temperature. However, the Seebeck coefficient of Ga increases from 0.2 to 2.1 µV/K, and thermal conductivity from 7.6 to 33 W/(K∙m). These electrical and thermal properties of Ga at solid–liquid phase transition would be useful for practical applications. PubDate: 2023-07-11
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Abstract: Implant-associated infections caused by biomedical catheters severely threaten patientsʼ health. The use of electrochemical control on NO release from benign nitrite equipped in the catheter can potentially resolve this issue with excellent biocompatibility. Inspired by nitrite reductase, a Cu-BDC (BDC: benzene-1,4-dicarboxylic acid) catalyst with coordinated Cu(II) sites was constructed as a heterogeneous electrocatalyst to control nitrite reduction to nitric oxide for catheter antibacteria. The combined results of in situ and ex situ tests unveil the key function of interconversion between Cu(II) and Cu(I) species in NO2− reduction to NO. After being incorporated into the actual catheter, the Cu-BDC catalyst exhibits high electrocatalytic activity toward NO2− reduction to NO and excellent antibacteria efficacy with a sterilizing rate of 99.9%, paving the way for the development of advanced metal–organic frameworks (MOFs) electrocatalysts for catheter antibacteria. Graphical PubDate: 2023-07-09
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Abstract: Abstract Electrocarboxylation of carbon dioxide (CO2) using organic substrates has emerged as a promising method for the sustainable synthesis of value-added carboxylic acids due to its renewable energy source and mild reaction conditions. The reactivity and product selectivity of electrocarboxylation are highly dependent on the cathodic behavior, involving a sequence of electron transfers and chemical reactions. Hence, it is necessary to understand the cathodic reaction mechanisms for optimizing reaction performance and product distribution. In this work, a review of recent advancements in the electrocarboxylation of CO2 with organic substrates based on different cathodic reaction pathways is presented to provide a reference for the development of novel methodologies of CO2 electrocarboxylation. Herein, cathodic reactions are particularly classified into two categories based on the initial electron carriers (i.e., CO2 radical anion and substrate radical anion). Furthermore, three cathodic pathways (ENE(N), ENED, and EDEN) of substrate radical anion-induced electrocarboxylation are discussed, which differ in their electron transfer sequence, substrate dissociation, and nucleophilic reaction, to highlight their implications on reactivity and product selectivity. PubDate: 2023-07-03
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Abstract: The interaction between a promoter and an active metal crucially impacts catalytic performance. Nowadays, the influence of promoter contents and species has been intensively considered. In this study, we investigate the effect of the iron (Fe)–zinc (Zn) proximity of Fe–Zn bimetallic catalysts on CO2 hydrogenation performance. To eliminate the size effect, Fe2O3 and ZnO nanoparticles with uniform size are first prepared by the thermal decomposition method. By changing the loading sequence or mixing method, a series of Fe–Zn bimetallic catalysts with different Fe–Zn distances are obtained. Combined with a series of characterization techniques and catalytic performances, Fe–Zn bimetallic proximity for compositions of Fe species is discussed. Furthermore, we observe that a smaller Fe–Zn distance inhibits the reduction and carburization of the Fe species and facilitates the oxidation of carbides. Appropriate proximity of Fe and Zn (i.e., Fe1Zn1-imp and Fe1Zn1-mix samples) results in a suitable ratio of the Fe5C2 and Fe3O4 phases, simultaneously promoting the reverse water–gas shift and Fischer–Tropsch synthesis reactions. This study provides insight into the proximity effect of bimetallic catalysts on CO2 hydrogenation performance. Graphical PubDate: 2023-06-21
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Abstract: Abstract The dehydrogenation of cyclohexanol to cyclohexanone is a crucial industrial process in the production of caprolactam and adipic acid, both of which serve as important precursors in nylon textiles. This endothermic reaction is constrained by thermodynamic equilibrium and involves a complex reaction network, leading to a heightened focus on catalysts and process design. Copper-based catalysts have been extensively studied and exhibit exceptional low-temperature catalytic performance in cyclohexanol dehydrogenation, with some being commercially used in the industry. This paper specifically concentrates on research advancement concerning active species, reaction mechanisms, factors influencing product selectivity, and the deactivation behaviors of copper-based catalysts. Moreover, a brief introduction to the new processes that break thermodynamic equilibrium via reaction coupling and their corresponding catalysts is summarized here as well. These reviews may offer guidance and potential avenues for further investigations into catalysts and processes for cyclohexanol dehydrogenation. PubDate: 2023-06-20
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Abstract: Abstract Short-chain perfluorocarboxylic acids (PFCAs) are a class of persistent organic pollutants that are widely used as substitutes for long-chain PFCAs. However, they also pose a non-negligible risk to ecosystems. In this study, we demonstrated that a fluorescent metal–organic framework (MOF) (named V-101) constructed from In3+ and an aromatic-rich tetratopic carboxylate ligand 5-[2,6-bis (4-carboxyphenyl) pyridin-4-yl] isophthalic acid (H4BCPIA) exhibited highly efficient turn-off and turn-on fluorescence responses toward five short-chain PFCAs in water and methanol, respectively. The limits of detection of V-101 toward five short-chain PFCAs are down to μg/L level, and it showed good anti-interference abilities toward short-chain PFCAs in the presence of common metal ions. The major mechanisms associated with fluorescence responses were molecular collisions and interactions between V-101 and short-chain PFCAs. This work demonstrates that the structure variety of MOFs imparts them with the potential of MOFs in the detection of short-chain PFCAs for pollution control. PubDate: 2023-06-16
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Abstract: Abstract Novel graphene-like boron nitride (BN)/Bi3O4Br photocatalysts have been controllably synthesized through a facile solvothermal method for the first time. Layer contact stacking between graphene-like BN and ultrathin Bi3O4Br was achieved with strong interaction. Dehalogenation is designed to harvest more visible light, and the ultrathin structure of Bi3O4Br is designed to accelerate charge transfer from inside to the surface. After graphene-like BN was engineered, photocatalytic performance greatly improved under visible light irradiation. Graphene-like BN can act as a surface electron-withdrawing center and adsorption center, facilitating molecular oxygen activation. O2•− was determined to be the main active species during the degradation process through analyses of electron spin resonance and XPS valence band spectra. PubDate: 2023-06-01
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Abstract: Abstract Around 60% of useful energy is wasted in industry, homes, or transportation. Therefore, there has been increasing attention on thermoelectric materials for their ability to harvest waste heat into useful energy. The efficiency of a thermoelectric material depends on its electrical conductivity, Seebeck coefficient, and thermal conductivity in a conflicting manner which results in efficiency optimization challenges. Single crystals and polycrystalline layered materials have comparatively better thermoelectric and mechanical properties in a certain direction. Texture engineering is a special strategy that allows the exploitation of superior material properties in a specific direction. Texturing could be achieved by various sintering and deformation methods, which yield defects improving thermoelectric and mechanical properties. The results show that for (Bi,Sb)2Te3, Bi2(Se,Te)3, CuSbSe2, and SnSe, significant enhancement in the thermoelectric figure of merit is achieved by enhancing the preferred orientation. Texture engineering provides a wide range of strategies to elevate the zT of anisotropic materials to values comparable to those of their single crystalline counterparts. PubDate: 2023-02-06
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Abstract: Abstract Over the past half-century, plastic consumption has grown rapidly due to its versatility, low cost, and unrivaled functional properties. Among the different implemented strategies for recycling waste plastics, pyrolysis is deemed the most economical option. Currently, the wax obtained from the pyrolysis of waste plastics is mainly used as a feedstock to manufacture chemicals and fuels or added to asphalt for pavement construction, with no other applications of wax being reported. Herein, the thermal pyrolysis of three common waste polyolefin plastics: high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP), was conducted at 450 °C. The waste plastics-derived waxes were characterized and studied for a potential new application: phase change materials (PCMs) for thermal energy storage (TES). Gas chromatography–mass spectrometry analysis showed that paraffin makes up most of the composition of HDPE and LDPE waxes, whereas PP wax contains a mixture of naphthene, isoparaffin, olefin, and paraffin. Differential scanning calorimetry (DSC) analysis indicated that HDPE and LDPE waxes have a peak melting temperature of 33.8 °C and 40.3 °C, with a relatively high latent heat of 103.2 J/g and 88.3 J/g, respectively, whereas the PP wax was found to have almost negligible latent heat. Fourier transform infrared spectroscopy and DSC results revealed good chemical and thermal stability of HDPE and LDPE waxes after 100 cycles of thermal cycling. Performance evaluation of the waxes was also conducted using a thermal storage pad to understand their thermoregulation characteristics for TES applications. PubDate: 2022-12-21
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