The nature of external surface barriers in the zeolite ZSM-5 was explored by comparing mass transfer of n -heptane in samples with different crystal sizes, surface structure, and composition. These different surface properties were achieved by HF acid etching and SiO 2 deposition on an as-synthesized ZSM-5 crystal sample. HF etching does not reduce surface barriers. SiO 2 deposition on the same sample reduces surface barriers significantly. These insights into the nature of surface barriers could be used to guide the rational design of zeolitic materials with better mass transport properties.
Increasing interest in aerogels among industrial sectors and the scientific community has sparked a sustained effort to develop methodologies for rational organization of aerogels for broader applications. Here we demonstrate that anisotropically compression-resilient cellulose/silica aerogels with tailorable macropores can be realized through guided self-assembly and controlled mineralization of bacterial cellulose. The cellulose/silica aerogels replicate the mesostructural features of modified bacterial cellulose with the macropores tailored during the biosynthesis using polystyrene spheres. Silica deposition surrounding bacterial cellulose nanofibers is controlled by moderating the hydrolysis and polycondensation of tetrapropoxysilane in the presence of cetyltrimethylammonium bromide. Cellulose/silica withstands 100 cycles with almost 100% height recovery along the growth direction and 1 cycle with 86.2% height recovery perpendicular to the growth direction at 60% compression strain. The anisotropic compression resilience is attributed to a multiscale deformation involving silica nanoparticles size, bead-on-string nanostructure, and oriented mesostructure of wavy fibers with cellular pores. The potential of the cellulose/silica aerogels for oily water cleansing is illustrated. Our work opens up new possibilities for bacterial cellulose-based advanced materials through in vivo mesostructure engineering and controlled mineralization.
Herein, Ga-ZnZrO x &ZSM-5 bifunctional catalysts were designed for CO 2 thermal hydrogenation to aromatics, particularly, aiming to enhance the selectivity of high-value BTX ( i.e. , benzene, toluene, and xylene). It was evident that the exterior surface properties and acidity of ZSM-5 can be effectively tailored by in-situ silicon deposition originating from the rice husk template. Catalytic performance assessments demonstrate an optimized catalyst achieving 88.1 % aromatics selectivity (exclusive CO) in a single pass, with a notable 45.2 % BTX selectivity within total aromatics and a low CO selectivity of 23.6 %. This superior performance is attributed to the in-situ silicon deposition on ZSM-5 during one-pot synthesis and the optimized spacing between Ga-ZnZrO x and ZSM-5 facilitated by the rice husk platform. Furthermore, in-situ DRIFTS analysis identifies key reaction intermediates. This study offers an effective strategy for tuning zeolite acidity using rice husks, while modulating metal oxide-zeolite proximity on the bio-SiO 2 platform, thus boosting CO 2 conversion to aromatics.
Impurities and carbon defects generally hinder practical application of microcrystalline graphite as anode material for lithium-ion batteries. However, the impurities and carbon defects of the natural microcrystalline graphite are found to be the active sites to catalyze silicon deposition during the chemical vapor deposition process. In this work, the impurities and carbon defects of prepared anode material are wrapped by double coatings that are combined by the silicon nanowires and the carbon layer. The composite anode material exhibits a high capacity of 640 mA h g −1 at a current density of 186 mA g −1 after 250 cycles. The results of the density functional theory calculation reveal that the existence of impurities and carbon defects on graphite surface enhances the absorption energy of graphite to silicon during chemical vapor deposition process at 900 °C. By utilizing the impurities and carbon defects, the natural microcrystalline graphite can be employed as a new and low-cost anode material to fabricate the high-performance lithium-ion batteries.
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