Herein, we report a novel carbothermal
welding strategy to prepare
atomically dispersed Pd sites anchored on a three-dimensional (3D)
ZrO2 nanonet (Pd1@ZrO2) via two-step
pyrolysis, which were evolved from isolated Pd sites anchored on linker-derived
nitrogen-doped carbon (Pd1@NC/ZrO2). First,
the NH2–H2BDC linkers and Zr6-based [Zr6(μ3-O)4(μ3-OH)4]12+ nodes of UiO-66-NH2 were transformed into amorphous N-doped carbon skeletons (NC) and
ZrO2 nanoclusters under an argon atmosphere, respectively.
The NC supports can simultaneously reduce and anchor the Pd sites,
forming isolated Pd1–N/C sites. Then, switching
the argon to air, the carbonaceous skeletons are gasified and the
ZrO2 nanoclusters are welded into a rigid and porous nanonet.
Moreover, the reductive carbon will result in abundant oxygen (O*)
defects, which could help to capture the migratory Pd1 species,
leaving a sintering-resistant Pd1@ZrO2 catalyst
via atom trapping. This Pd1@ZrO2 nanonet can
act as a semi-homogeneous catalyst to boost the direct synthesis of
indole through hydrogenation and intramolecular condensation processes,
with an excellent turnover frequency (1109.2 h–1) and 94% selectivity.
With the rise of renewable energy resources, especially offshore wind power plant, the DC transmission concept has attracted more and more attention. The selection of eco‐friendly insulating gas, as most critical insulating part of gas‐insulated equipment is top priority for developing highly reliable system. Moreover, it is acknowledged that eco‐friendly C3F7CN/CO2 gas mixtures have become a potential alternative to SF6 gas due to its excellent performance. This study reviews the basic physical properties of C3F7CN gas/gas mixtures and insulation properties including the gas gap breakdown and surface flashover performance at DC, as well as lightning impulse voltage. Investigation about the gas stability is presented, including the compatibility of gas with solid materials in gas‐insulated transmission line (GIL), and the decomposition characteristics under long‐term electrical and thermal stresses. The important progress on the charge accumulation characteristics of gas–solid interface in the novel gas environment under DC voltage stress is analysed. Finally, the key issues that need to be paid attention to and further followed through regarding the application of this novel gas in GIL are summarised and put forward. This study hopefully can provide a complete reference for the development of eco‐friendly DC gas insulation equipment with C3F7CN/CO2 gas mixtures.
The catalytic properties of supported metal heterostructures critically depend on the design of metal sites. Although it is well-known that the supports can influence the catalytic activities of metals, precisely regulating the metal-support interactions to achieve highly active and durable catalysts still remain challenging. Here, the authors develop a support effect in the oxide-supported metal monomers (involving Pt, Cu, and Ni) catalysts by means of engineering nitrogen-assisted nanopocket sites. It is found that the nitrogen-permeating process can induce the reconstitution of vacancy interface, resulting in an unsymmetrical atomic arrangement around the vacancy center. The resultant vacancy framework is more beneficial to stabilize Pt monomers and prevent diffusion, which can be further verified by the density functional theory calculations. The final Pt-N/SnO 2 catalysts exhibit superior activity and stability for HCHO response (26.5 to 15 ppm). This higher activity allows the reaction to proceed at a lower operating temperature (100 °C). Incorporated with wireless intelligent-sensing system, the Pt-N/SnO 2 catalysts can further achieve continuous monitoring of HCHO levels and cloudbased terminal data storage.
Engineering the local three-dimensional structure of metal sites has important effect to maximize the activity and selectivity of single-atom site catalysts. Here, we engineer a strain-assisted single Pt sites structure on highly curved MoS 2 surface to enhance the H 2 S sensor property. Through introducing N-methyl-2-pyrrolidone (NMP) as guiding molecules, a multilayer MoS 2 structure with bending base planes is achieved. This bending behavior can not only inject uniform in-plane strain into the original inert MoS 2 basal plane but also introduce sufficient accessible sites to anchor Pt monomers. Further experimental and theoretical results show that the high-curvature MoS 2 surface endows 0.8% stretch strain onto the low-coordinated single Pt sites with a unique "tip" effect, which will lead to more accumulation of electrons around the Pt species, thus accelerating the electric transfer process between H 2 S and supports. The final catalyst delivers the pronouncedly enhanced H 2 S
Hydrogen separation membranes are a critical component
in the emerging
hydrogen economy, offering an energy-efficient solution for the purification
and production of hydrogen gas. Inspired by the recent discovery of
monolayer covalent fullerene networks, here we show from concentration-gradient-driven
molecular dynamics that quasi-square-latticed monolayer fullerene
membranes provide the best pore size match, a unique funnel-shaped
pore, and entropic selectivity. The integration of these attributes
renders these membranes promising for separating H2 from
larger gases such as CO2 and O2. The ultrathin
membranes exhibit excellent hydrogen permeance as well as high selectivity
for H2/CO2 and H2/O2 separations,
surpassing the 2008 Robeson upper bounds by a large margin. The present
work points toward a promising direction of using monolayer fullerene
networks as membranes for high-permeance, selective hydrogen separation
for processes such as water splitting.
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