Search

Wide band gap metal oxide semiconductor catalysts mostly exhibit very huge variations of catalytic reaction activities and pathways depending on the preparation conditions, unlike metallic catalyst materials. Atomic-scale modeling and ab initio calculations are extremely challenging for metal oxide semiconductor catalysts because of two main reasons: (i) large discrepancies between computational predictions and experiments, (ii) typical cell size limitations in modeling for dilute level doping (<1020 cm−3) cocatalyst size-dependency (diameter >3 nm). In this study, as a new groundbreaking methodology, we used a combination of density functional theory (DFT) calculations and a newly derived analytical model to systematically investigate the mechanisms of catalytic methane (CH4) oxidation activity change of CeO2. The key hypothesis that the catalytic methane oxidation reaction can be followed by the Fermi level change in CeO2 was well demonstrated via comparison with our multi-scale simulation and several literature reports. Our new method was found to give predictions in the catalytic activity of wide band gap semiconductors for variations in defect concentrations and cocatalyst coverage with advanced efficiency and accuracy, overcoming the typical model size limitation and inaccuracy problems of DFT calculations. [ABSTRACT FROM AUTHOR]

Electrochemical nitrogen reduction reaction (NRR) is a sustainable alternative to the Haber‒Bosch process for ammonia (NH3) production. However, the significant uphill energy in the multistep NRR pathway is a bottleneck for favorable serial reactions. To overcome this challenge, we designed a vanadium oxide/nitride (V2O3/VN) hybrid electrocatalyst in which V2O3 and VN coexist coherently at the heterogeneous interface. Since single‐phase V2O3 and VN exhibit different surface catalytic kinetics for NRR, the V2O3/VN hybrid electrocatalyst can provide alternating reaction pathways, selecting a lower energy pathway for each material in the serial NRR pathway. As a result, the ammonia yield of the V2O3/VN hybrid electrocatalyst was 219.6 µg h−1 cm−2, and the Faradaic efficiency was 18.9%, which is much higher than that of single‐phase VN, V2O3, and VNxOy solid solution catalysts without heterointerfaces. Density functional theory calculations confirmed that the composition of these hybrid electrocatalysts allows NRR to proceed from a multistep reduction reaction to a low‐energy reaction pathway through the migration and adsorption of intermediate species. Therefore, the design of metal oxide/nitride hybrids with coherent heterointerfaces provides a novel strategy for synthesizing highly efficient electrochemical catalysts that induce steps favorable for the efficient low‐energy progression of NRR. [ABSTRACT FROM AUTHOR]

Porosification of fluoride can be effectively utilized in various applications, based on its abundance of exposed active sites. However, previous approaches have drawbacks in terms of application in fields that require meticulous control over porosity. Herein, an innovative strategy is suggested for achieving precise porosity tuning using a micelle‐carried MgF2 precursor intermediate. As the size of the MgF2 precursor clusters increases through micellization, the sizes of the resulting solidified MgF2 grains and the intergranular voids between the grains increase. Controlled MgF2 with intergranular voids can achieve very low‐refractive indices (≈1.04) with extremely fine refractive index control intervals (0.01–0.04). By employing extreme controllability of refractive index, graded refractive index antireflective coating is applied to the quartz window, and an average transmittance of ≈97.96% (250–1100 nm) is obtained. Finally, the coating is applied to a perovskite half‐cell enabling a ≈22.46% increase in the light‐absorption efficiency. [ABSTRACT FROM AUTHOR]

The performances of five cellulosic polymers with different functional groups (cellulose, cellulose acetate, cellulose phosphate, chitosan, and chitin) as sorbents of seven frequently used hazardous polar organic liquids (acrolein, butanone peroxide, epichlorohydrin, formaldehyde, furfuryl alcohol, propylene oxide, and vinyl acetate) are investigated in this study. Amongst the cellulosic sorbents, cellulose phosphate exhibited enhanced sorption properties (as high as 3.09–7.03 g/g) against all seven polar organic liquids investigated, and chitosan and chitin also demonstrated comparable sorption efficiencies (2.28–7.72 g/g and 2.55–5.86 g/g, respectively) to those of cellulose phosphate. According to our investigation, the enhanced sorption efficiency could be achieved due to low powder density of cellulose phosphate, which is caused by the weak intramolecular interaction amongst the polymer chains. In addition, cellulose phosphate, chitosan, and chitin also showed enhanced absorbed solvent recovery percents (71.4, 60.6, and 61.1%, respectively, in average) compared with that of pristine cellulose (43.8%). With excellent sorption efficiency, enhanced solvent recovery rate, and reusability after drying, these functionalized cellulosic sorbents can be excellent candidates to replace the conventional carbon and vermiculites-based sorbents, especially for liquid polar organic spill sorption. [ABSTRACT FROM AUTHOR]

Although energy‐storage devices based on Li ions are considered as the most prominent candidates for immediate application in the near future, concerns with regard to their stability, safety, and environmental impact still remain. As a solution, the development of all‐solid‐state energy‐storage devices with enhanced stability is proposed. A new eco‐friendly polymer electrolyte has been synthesized by incorporating lithium trifluoromethanesulfonate into chemically modified methyl cellulose (LiTFS–LiSMC). The transparent and flexible electrolyte exhibits a good conductivity of near 1 mS cm−1. An all‐solid‐state supercapacitor fabricated from 20 wt % LiTFS–LiSMC shows comparable specific capacitances to a standard liquid‐electrolyte supercapacitor and an excellent stability even after 20 000 charge–discharge cycles. The electrolyte is also compatible with patterned carbon, which enables the simple fabrication of micro‐supercapacitors. In addition, the LiTFS–LiSMC electrolyte can be recycled and reused more than 20 times with negligible change in its performance. Thus, it is a promising material for sustainable energy‐storage devices. [ABSTRACT FROM AUTHOR]