Tuning
the atomic interface configuration of noble metals (NMs)
and transition-metal oxides is an effective straightforward yet challenging
strategy to modulate the activity and stability of heterogeneous catalysts.
Herein, Pd supported on mesoporous Fe2O3 with
a high specific surface area was rationally designed and chosen to
construct the Pd/iron oxide interface. As a versatile model, the physicochemical
environments of Pd nanoparticles (NPs) could be precisely controlled
by taming the reduction temperature. The experimental and density
functional theory calculation results unveiled that the catalyst in
the support–metal interface confinement (SMIC) state showed
significantly enhanced catalytic activity and sintering resistance
for CO oxidation. The constructed Fe sites at the interfaces between
FeO
x
overlayers and Pd NPs not only provided
additional coordinative unsaturated ferrous sites for the adsorption
and activation of O2, thereby facilitating the activation
efficiency of O2, but also impressively changed the reaction
pathway of CO oxidation. As a result, the catalyst followed the Pd/Fe
dual-site mechanism instead of the classical Mars–van Krevelen
mechanism. For the catalyst in the strong metal–support interaction
(SMSI) state, its catalytic activity was seriously suppressed because
of the excessive encapsulation of the active Pd sites by FeO
x
overlayers. The present study therefore provides
detailed insights into the SMIC and SMSI in ferric oxide-supported
Pd catalysts, which could guide the preparation of highly efficient
supported catalysts for practical applications.
Noble-metal-free
photocatalyst Co2P-CdS was synthesized
via a facile in situ hydrothermal method for the first time to boost
the performance of photocatalytic H2 production. This synthesis
process allows the Co2P nanoparticles to disperse evenly
on the surface of CdS sub-microspheres and to form unique intimate
contact interfaces. The physical and photophysical properties of as-prepared
Co2P-CdS composite samples were characterized by X-ray
diffractometry, transmission electron microscopy, UV–vis diffusion
reflectance spectroscopy, X-ray photoelectron spectroscopy, photoluminescence,
and surface photovoltage (SPV) spectroscopy. The results indicate
that the photocatalytic H2 evolution activity of CdS sub-microspheres
under visible-light irradiation is significantly enhanced by introducing
inexpensive Co2P as co-catalyst. The Co2P-CdS
sample with a loading of 1.2 mol% Co2P gives the highest
H2 production rate of 0.303 mmol·h–1, which was about 3 times higher than that achieved with 0.5 wt%
Pt-loaded CdS sample. After further introduction of K2HPO4 as sacrificial agent, the H2 production rate reached
0.356 mmol·h–1, which is 41 times higher than
that obtained with pure CdS. The apparent quantum yield of the Co2P-decorated CdS sample is about 13.88% at 420 nm. These results
suggest that the synergistic effect between Co2P and CdS
greatly enhances the photocatalytic activity of CdS. Moreover, a reasonable
mechanism for the enhanced photocatalytic activity was proposed through
density functional theory calculation and verified by SPV spectroscopy.
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