Mass transfer can tune the surface concentration of reactants and products and subsequently influence the catalytic performance. The morphology of nanomaterials plays an important role in the mass transfer of reaction microdomains, but related studies are lacking. Herein, a facile electrospinning technique utilizing cellulose was employed to fabricate a series of carbon nanofibers with different diameters, which exhibited excellent electrochemical nitrate reduction reaction and oxygen evolution reaction activities. Furthermore, the microstructure of electrocatalysts could influence the gas–liquid–solid interfacial mass transfer, resulting in different electrochemical performances.
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.
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.
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.
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.
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 IrO x and CeO2 (IrO x/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 IrO x/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 IrO x 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.