Over the past decade, considerable progress has been made in the synthesis and applications of nanoporous carbon spheres ranging in size from nanometres to micrometres. This Review presents the primary techniques for preparing nanoporous carbon spheres and the seminal research that has inspired their development, presented potential applications and uncovered future challenges. First we provide an overview of the synthesis techniques, including the Stöber method and those based on templating, self-assembly, emulsion and hydrothermal carbonization, with special emphasis on the design and functionalization of nanoporous carbon spheres at the molecular level. Next, we cover the key applications of these spheres, including adsorption, catalysis, separation, energy storage and biomedicine ? all of which might benefit from the regular geometry, good liquidity, tunable porosity and controllable particle-size distribution offered by nanoporous carbon spheres. Finally, we present the current challenges and opportunities in the development and commercial applications of nanoporous carbon spheres.
Here, we report the synthesis of mesoporous ZnO/Ni@m-SiO2 yolk-shell particles. The unique ZnO/Ni@m-SiO2 catalysts demonstrate impressive resistance to sintering and coking for dry reforming of methane (DRM). They also display long term stability with high levels of conversion and selectivity, making this catalyst promising for chemical CO2 upgrading.
The hydrogenation of levulinic acid to ³-valerolactone with water as solvent is a crucial
reaction for producing fine chemicals. However, the development of highly stable catalysts is
still a major challenge. Here, we prepared a Ru nanoparticles incorporated in mesoporous-carbon
(Ru-MC) catalyst to achieve high stability in acidic aqueous medium. The Ru-MC showed
excellent catalytic performance (12024h-1 turnover frequency) in the hydrogenation of LA-to3
GVL. Compared with Ru supported on mesoporous carbon catalyst (Ru/MC) prepared by
conventional wet impregnation method, the Ru-MC showed excellent reusability (more than 6
times) and thermal stability (up to 600 oC). Based on H2-TPR-MS characterization, it was
proposed that the incorporated structure significantly increased the interaction between Ru
nanoparticles and carbon support, which effectively prevent the leaching and sintering of Ru
nanoparticles and contributed to increased high reusability and thermal stability of the Ru-MC.
Encapsulation of metal nanoparticles is a leading technique used to inhibit the main deactivation mechanisms in dry reforming of methane reaction (DRM): Carbon formation and Sintering. Ni catalysts (15%) supported on alumina (Al2O3) and ceria (CeO2) have shown they are no exception to this analysis. The alumina supported catalysts experienced graphitic carbonaceous deposits, whilst the ceria showed considerable sintering over 15 h of DRM reaction. The effect of encapsulation compared to that of the performance of uncoated catalysts for DRM reaction has been examined at different temperatures, before conducting longer stability tests. The encapsulation of Ni/ZnO cores in silica (SiO2) leads to advantageous conversion of both CO2 and CH4 at high temperatures compared to its uncoated alternatives. This work showcases the significance of the encapsulation process and its overall effects on the catalytic performance in chemical CO2 recycling via DRM.