Enhanced charge carrier generation, attenuated exciton-effect as well as upgraded CO2 adsorption/activation lead to a promoted CO2-to-CO photocatalytic conversion ability for C-vacancy modified GCN.
Bulk metal doping and surface phosphate
modification were synergically
adopted in a rational design to upgrade the CeO2 catalyst,
which is highly active but easily deactivated for the catalytic oxidation
of chlorinated volatile organic compounds (Cl-VOCs). The metal doping
increased the redox ability and defect sites of CeO2, which
mostly promoted catalytic activity and inhibited the formation of
dechlorinated byproducts but generated polychlorinated byproducts.
The subsequent surface modification of the metal-doped CeO2 catalysts with nonmetallic phosphate completely suppressed the formation
of polychlorinated byproducts and, more importantly, enhanced the
stability of the surface structure by forming a chainmail layer. A
highly active, durable, and selective catalyst of phosphate-functionalized
RuO
x
–CeO2 was the most
promising among all the metal-doped (Ru, Pd, Pt, Cr, Mn, Fe, Co, and
Cu) CeO2 catalysts investigated owing to the prominent
chemical stability of RuO
x
and its superior
versatility in the catalytic oxidation of different kinds of Cl-VOCs
and other typical pollutants, including dimethyl sulfide, CO, and
C3H8. Moreover, the chemical stability of the
catalyst, including its bulk and surface structural stability, was
investigated by combining intensive treatment with HCl/H2O or HCl with subsequent ex situ ultraviolet–visible light
Raman spectroscopy and confirmed the superior resistance to Cl poisoning
of the phosphate-functionalized RuO
x
–CeO2. This work exemplifies a promising strategy for developing
ideal catalysts for the removal of Cl-VOCs and provides a catalyst
with the superior catalytic performance in Cl-VOC oxidation to date.
layered MnO 2 materials, composed of exotic electronic properties and accessible active sites with alkali metal ions, provide a comprehensive platform for developing catalysts with chemical modification. Significantly, K + -contained layered MnO 2 catalysts have been verified as strong candidates toward catalytic oxidation of formaldehyde (HCHO). Unveiling the effects of alkali metal ions on active sites is critical to understand the interaction between reactants and active centers. Through a combination of analytical tools with periodic computational density functional theory modeling, the surface structures and the exposing specific defects of alkali metal ions affiliated to oxygen vacancies (Vo) are figured out by comparing three typical alkali metal ionintercalated (Na + , K + , and Cs + ) layered MnO 2 materials. These materials have been synthesized via a molten salt method, with high yield, large lateral size, and nanometer thickness in a few moments. We demonstrate that the alkali metal ions could remarkably alter the formation energy of Vo by the sequence of CsMnO (1.94 eV) < KMnO (1.97 eV) < NaMnO (2.07 eV) < ideal MnO 2 surface without the intercalated ion (2.23 eV). As a result, CsMnO with the most surface Vo sites could achieve efficient HCHO oxidation to CO 2 , with a HCHO consumption rate of about 0.149 mmol/(g•h) at 40 °C in 200 ppm HCHO/humid air [gas hourly space velocity = 80,000 mL/(g•h)]. Different from the Mars−van-Krevelen process, quantum chemical calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy revealed that the main reaction pathway might be HCHO(ad) + [O](ad) → DOM → [HCOO − ] s → CO 2 via a Langmuir−Hinshelwood (L−H) mechanism. Alkali metals remarkably promoted the HCHO conversion by trapping oxygen through Vo sites and accelerating the facile reaction among adsorbed oxygen with adsorbed HCHO to deep degradation products (CO 2 and H 2 O).
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