ABSTRACT
3D composite electrodes have shown extraordinary promise as high mass loading electrode materials for sodium ion batteries (SIBs). However, they usually show poor rate performance due to the sluggish Na+ kinetics at the heterointerfaces of the composites. Here, a 3D MXene-reduced holey graphene oxide (MXene-RHGO) composite electrode with TiâOâC bonding at 2D heterointerfaces of MXene and RHGO is developed. Density functional theory (DFT) calculations reveal the built-in electric fields (BIEFs) are enhanced by the formation of bridged interfacial TiâOâC bonding, that lead to not only faster diffusion of Na+ at the heterointerfaces but also faster adsorption and migration of Na+ on the MXene surfaces. As a result, the 3D composite electrodes show impressive properties for fast Na+ storage. Under high current density of 10 mA cm-2, the 3D MXene-RHGO composite electrodes with high mass loading of 10 mg cm-2 achieve a strikingly high and stable areal capacity of 3 mAh cm-2, which is same as commercial LIBs and greatly exceeds that of most reported SIBs electrode materials. The work shows that rationally designed bonding at the heterointerfaces represents an effective strategy for promoting high mass loading 3D composites electrode materials forward toward practical SIBs applications.
ABSTRACT
The selective oxidation of biobutanol to prepare butyric acid is an important conversion process, but the preparation of low-temperature and efficient catalysts for butanol oxidation is currently a bottleneck problem. In this work, we prepared Pt-TiO2 catalysts with different Pt particle sizes using a simple one-step hydrothermal/solvothermal method. Transmission electron microscopy and X-ray diffraction results showed that the average size of the Pt particles ranged from 1.1 nm to 8.7 nm. Among them, Pt-TiO2 with an average particle size of 3.6 nm exhibited the best catalytic performance for biobutanol. It was capable of almost completely converting butanol, even at room temperature (30 °C), with a 98.9% biobutanol conversion, 98.4% butyric acid selectivity, and a turnover frequency (TOF) of 36 h-1. Increasing the reaction temperature to 80 and 90 °C, the corresponding TOFs increased rapidly to 355 and 619 h-1. The relationship between the electronic structure of Pt and its oxidative performance suggests that the synergistic effect of the dual sites, Pt0 and Pt2+, could be the primary factor contributing to its elevated reactivity.
ABSTRACT
During the operation of the boiler, the ash deposition phenomenon in the furnace will cause abnormal operation of the boiler system. This will lead to an increase the pollutant emission. To relieve the pollutant emission during the abnormal operation of the boiler, the mechanism of ash deposition was investigated from the perspective of reducing the phenomenon for ash deposition in this paper. Calcium-containing compounds play an important role in ash deposition burning coal. Therefore, the influence of calcium-containing compounds on ash deposition was investigated with Zhundong coal in a horizontal tube furnace in this paper. Furthermore, the binding and diffusion properties of calcium-containing compounds on the oxide film's surface were characterized under different temperatures by molecular dynamics simulations. The growth process of surface crystals was also researched by kinetic Monte Carlo method. The results indicated the precipitation rate of calcium gradually increases with the increase of combustion temperature. CaO, CaSO4, and CaSiO3 can play an important role in ash deposition burning Zhundong coal. CaSO4 is more easily to react with α-Fe2O3 (110) than CaO or CaSiO3. The diffusion coefficient of CaSO4, CaO, or CaSiO3 increases gradually with the increase of temperature. Furthermore, the system composed of CaSO4 and oxide film is more affected by temperature than that of CaO or CaSiO3 and oxide film. Moreover, under the whole temperature, the content of CaSO4 on the surface of the oxide film is the most. Finally, three calcium-containing minerals can promote each other during the deposition process and accelerate the formation of ash deposits.
