Xicheng Ma

Growth and microstructure of Co-filled carbon nanotubes

Cobalt-filled carbon nanotubes were prepared in situ in the decomposition of benzene over Co/silica-gel catalysts. Unlike the previous reports, in our experiments, the catalysts need not pre-reduced. Transmission electron microscopy (TEM) investigation showed that the as-made products contained abundance of carbon nanotubes (CNTs) and almost 100% of them were filled with metallic nanoparticles or nanorods. High-resolution TEM (HRTEM), selected area electron diffraction (SAED) patterns and energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Co inside the nanotubes. The encapsulated Co was further identified as alpha-Co with face-centered cubic (fcc) structure, which frequently consists of twinned boundaries. Based on the experimental results, a possible growth mechanism of the Co-filled nanotubes was proposed.

Microstructural features of Co-filled carbon nanotubes

Cobalt-filled carbon nanotubes (CNTs) were prepared in situ in the decomposition of benzene over Co/silica-gel catalysts. Transmission electron microscopy (TEM) investigation showed that the products contained abundance of carbon nanotubes and most of them were filled with metallic nanoparticles or nanorods. High-resolution TEM (HRTEM), selected area electron diffraction (SAED) patterns and energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Co inside the nanotubes. The encapsulated Co was further identified as α-Co with fcc structure, which frequently consists of twinned boundaries. Based on the experimental results, a possible growth mechanism of the Co-filled nanotubes was proposed.

The Potential of Cu‐SAPO‐44 in the Selective Catalytic Reduction of NOx with NH3

Nitrogen oxides (NOx) contribute much to acid rain, photochemical smog, and the depletion of tropospheric ozone. A novel, small‐pore Cu‐exchanged chabazite (Cu‐CHA) zeolite, Cu‐SAPO‐44, was first studied for the selective catalytic reduction of NOx with ammonia (NH3‐SCR), and exhibits excellent activity and N2 selectivity over the wide temperature window from 200–550 °C. The Cu content in Cu‐SAPO‐44 plays a significant role in the NH3‐SCR reactions. Two kinds of isolated Cu2+ species inside the large cages and in the six‐membered rings of the CHA structure were verified as the active sites, which are responsible for the low‐temperature and high‐temperature activity, respectively. Cu‐SAPO‐44 is shown to be a promising candidate as a SCR catalyst for deNOx with great potential in after‐treatment systems for either mobile or stationary sources.

Hydrophobic W18O49 mesocrystal on hydrophilic PTFE membrane as an efficient solar steam generation device under one sun

Solar steam generation is a promising application for utilizing exhaustless solar energy for steam generation, desalination, sterilization, and water treatment. Over the past several decades, scientists have made many attempts to design rational structures to promote evaporation efficiency including optimizing optical absorption, photothermal conversion, heat localization, and water transportation. Here, an efficient solar steam generation device was fabricated through decorating a nonstoichiometric W18O49 mesocrystal, as a solar light-to-heat material, onto a hydrophilic PTFE membrane. Nonstoichiometric W18O49 mesocrystals were incorporated into the membrane, and confirmed by the XRD, SEM, TEM, and XPS characterizations, which can transfer light to heat after absorbing sunlight and lead to water evaporation on a local area of a membrane. The structure of the solar steam generation device was confirmed by the results of SEM and contact angle measurements, which insured the solar steam generation device self-floated on top of water, thereby providing a continuous water supply to the local area heated by the W18O49 mesocrystals from bulk water. Under one sun illumination, the evaporated water mass loss reached 1.13 kg m−2 for a membrane thickness of M/A = 9.83 g m−2 after 1 h irradiation, and the membrane showed a high efficiency of 80.7%. Limit of water evaporation rate for the W18O49@PDMS mesocrystal membrane was further calculated to be 1.15 kg m−2 after 1 h one-sun irradiation, with a limit of efficiency of 82.0%. The salinities of simulated seawater reduced to levels far below the World Health Organizations (WHO) standard after desalination. The rational design enhancing evaporation performance also provides enlightenment for further practical applications of solar steam generation technology.