Search

• A novel core–shell CM-P was prepared via a facile cation-driven electrostatic self-assembly strategy. • The charge redistribution in CM-P heterostructures was observed. • The CM-P cathodes exhibited a high specific capacity of 260 mAh/g. • The CM-P//Zn ZISCs showed a high energy density of 217.1 Wh kg−1 along with power density of 22.3 kW kg−1. Rechargeable aqueous Zn-ion hybrid supercapacitors (ZISCs) with the superiorities of high theoretical capacity, low redox potential and aqueous electrolytes with superior ionic conductivity (∼1 S cm−1) are promising energy storage systems. However, a primary concern persists due to the absence of cathode materials with both high energy densities and satisfactory cycling stability for robust ZISCs. In this study, we design a spherical core–shell covalent organic frameworks@Ti 3 CN MXene (CM-P) cathode via a cation-driven electrostatic self-assembly strategy. The CM-P with the constructed heterostructures shows both well-organized pore channels and excellent intrinsic conductivity, facilitating fast accessibility to intrinsic redox-active sites (such as C = O and N), and promoting effective ion diffusion characterized by low energy barriers. Consequently, the CM-P cathodes demonstrate excellent electrochemical performance, featuring an ultrahigh specific capacity of 260 mAh/g at 0.1 A, a high-rate capability with 68 % retention at 1 A/g, and long-term cycling stability. First-principle calculations elucidate that the enhanced charge-storage mechanism relies on the heterostructures of CM-P, accelerating ion adsorption/diffusion and electron transfer. Furthermore, the assembled CM-P//Zn ZISCs devices show a high energy density of 217.1 Wh kg−1 along with power density of 22.3 kW kg−1. This work provides an innovative approach to design COFs-based heterostructures for advanced ZISCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eruption of the rising bubbles causes the sand particles to be elutriated. • Lateral fuel injection leads to a non-uniform distribution of fluxes and gas species. • Temperature variation at z = 0.5 m leads to the sudden changes in gas thermal properties. • The HTC of sand particles ranges from 80 to 200 W/(m2·K) in the BFBG. • Sand particles have a larger Rep in the bubble phase but a smaller Rep in the dense phase. A reactive multiphase particle-in-cell approach is developed to explore the air-blown coal gasification in a bubbling fluidized bed reactor. The model is validated by comparing the predicted bed hydrodynamics and product yields with experimental data. Subsequently, the gas thermal properties and particle-scale behaviours are comprehensively explored. The results show that: (i) the density difference between two solid species gives rise to spatial segregation, which further affects the gasification process. The presence of coal feeding port causes the non-uniform distribution of bed hydrodynamics. (ii) the combustible gases species distribute above the coal feeding port. The concentration of gas species continuously increases while the gas temperature changes little in the dense region. (iii) the slip velocity of sand particles ranges from 0 to 4 m/s; the temperature ranges from 1000 K to 1150 K, and the heat transfer coefficient ranges from 80 W/(m2·K) to 200 W/(m2·K). Compared with sand, coal particles have a larger heat transfer coefficient and particle Reynolds number (Rep). Coal particles reach the maximum temperature of about 1100 K in the period of 3 s after being injected into the bed. (iv) bubble and emulsion phases give a larger Rep and smaller Rep due to the dominant role of the interphase drag force and inter-particle collision force, respectively. [ABSTRACT FROM AUTHOR]