High-entropy perovskite fluorides
(HEPFs) have great potential
in electrocatalysis that has not been realized because of the limitation
of a high-temperature synthetic route and the limited understanding
of high-entropy materials. The use of HEPFs in effective oxygen evolution
catalysis and a feasible synthesis route for HEPFs in a boiled solution
by combining a hydrothermal method with mechanochemistry are first
reported here. These HEPFs consisting of cost-effective elements dramatically
gave excellent catalytic activity for the oxygen evolution reaction
in an alkaline media.
Strong metal−support interaction (SMSI) construction is a pivotal strategy to afford thermally robust nanocatalysts in industrial catalysis, but thermally induced reactions (>300 °C) in specific gaseous atmospheres are generally required in traditional procedures. In this work, a photochemistry-driven methodology was demonstrated for SMSI construction under ambient conditions. Encapsulation of Pd nanoparticles with a TiO x overlayer, the presence of Ti 3+ species, and suppression of CO adsorption were achieved upon UV irradiation. The key lies in the generation of separated photoinduced reductive electrons (e − ) and oxidative holes (h + ), which subsequently trigger the formation of Ti 3+ species/oxygen vacancies (O v ) and then interfacial Pd−O v −Ti 3+ sites, affording a Pd/TiO 2 SMSI with enhanced catalytic hydrogenation efficiency. The as-constructed SMSI layer was reversible, and the photodriven procedure could be extended to Pd/ZnO and Pt/TiO 2 .
One
of the grand challenges in industrial catalytic processes is
the inevitable sintering and aggregation of conventional supported
catalysts to large particles, leading to the decrease of activity
and even deactivation with time. Herein, a surface spatial confinement
strategy was employed to design high-performing catalysts for the
dry reforming of methane (DRM). Specifically, active nickel (Ni) nanoparticles
(NPs) were confined on the surface of a dendritic mesoporous silica
(DMS) in the form of the “catalysts in coronas”. The
Ni/DMS catalyst exhibited a high catalytic performance close to its
equilibrium conversion (76% conversion for CH4 at 700 °C).
More importantly, the prepared catalyst remained stable after 145
h time-on-stream at 700 °C without noticeable carbon deposition.
This sintering and coking resistance was found to arise from the surface
spatial confinement effect in which the three-dimensional dendritic
layers in the corona posted a steric barrier against migration and
aggregation of Ni NPs and size of Ni NPs was controlled below 5 nm,
hence against sintering and coking. Meanwhile, the mesoporous feature
of the layered wall facilitated mass transport of reactants to Ni
species and further boosted catalysis. This strategy should be broadly
applicable to a range of metal- and metal oxide-supported catalysts
in high-temperature heterogeneous reactions, such as DRM, water gas
shift reaction, and vehicle emission control related reactions.
The
partial or complete blockage of active sites of metal nanoparticles
(NPs) on supported-metal catalysts has been of interest for tuning
the stability, selectivity, and rate of reactions. Here, we show that
Au-sites in Au/TiO2 surprisingly become blocked upon treatment
in common alcohols (2-propanol and methanol), with 2-propanol causing
a greater extent of blockage. Nearly 95% of Au-sites are covered after
treatment in 2-propanol at room temperature, followed by desorption
at 150 °C. Infrared spectroscopy of CO adsorption unambiguously
confirms the occurrence of this phenomenon. Electron energy loss spectroscopy
(EELS), temperature-programmed desorption (TPD), Raman spectroscopy,
and DFT simulations suggest that the formation of carbon deposits
from 2-propanol decomposition and/or the migration of a TiO
x
layer over the supported NPs may be responsible
for the blockage of Au-sites. Nearly full coverage of Au NPs after
treatment in 2-propanol led to negligible activity for catalytic CO
oxidation, whereas partial retraction of the overlayer led to enhanced
activity with time-on-stream, suggesting a self-activating catalytic
performance.
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