Copper-cobalt Bimetallic Oxides-doped Alumina Hollow Spheres: A Highly Efficient Catalyst for Epoxidation of Styrene

Instant and quantitative epoxidation of styrene under ambient conditions over a nickel(ii)dibenzotetramethyltetraaza[14]annulene complex immobilized on amino-functionalized SBA-15

Nickel(ii)dibenzotetramethyltetraaza[14]annulene complex (Nitmtaa) was synthetized and immobilized on post amino-functionalized SBA-15 (N-SBA-15) to obtain a stable and reusable nanocatalyst named as Nitmtaa@N-SBA-15. Here (3-aminopropyl)triethoxysilane (APTES) was first grafted on the surface SBA-15, then Nitmtaa was added and coordinated on the silica surface via APTES amine groups. The structure and morphology, and thermal stability of the prepared nanocatalyst was investigated using SEM, HR-TEM, BET, FT-IR, powder XRD, and TGA. HR-TEM and XRD results revealed a high dispersion of Nitmtaa on the SBA-15 surface. The catalytic activity of this nanocatalyst was evaluated in the epoxidation of styrene, under ambient conditions, using meta-chloroperoxybenzoic acid (m-CPBA) as the oxygen donor. This nanocatalyst showed an immediate and quantitative epoxidation of styrene with high turn-over-frequency ∼31.58 s-1. Moreover, the superior catalytic activity and high stability of Nitmtaa@N-SBA-15 could be maintained after four successive cycles. A possible reaction mechanism is also proposed.

Hollow multishelled structures revive high energy density batteries

Hollow structures have been shown to be fruitful in addressing the cycling-stability problem of high-capacity electrode materials. However, we have noticed that there exist misconceptions toward the energy density of hollow-structured electrodes. In this Focus Article, the indispensability of hollow structures for stable high energy density batteries is discussed. Additionally, the merits of hollow multishelled structures (HoMSs) superior to their single-shelled counterparts mainly including optimizing the volumetric energy density, improving the mechanical robustness and enabling smart safe energy-storage behaviors have also been highlighted. The goal of the current article is to clarify that a HoMS-based electrode is indispensable to realize a practically high energy density in addition to lengthening the cycling lifespan and guide the future development of HoMSs to further improve the performance of rechargeable batteries.