Influence of Support and Metal Precursor on the State and CO Catalytic Oxidation Activity of Platinum Supported on TiO₂

The influence of the nature of TiO₂ support and platinum salt precursors on the state and CO catalysis oxidation activity of supported platinum on TiO₂ was investigated in this paper. Variations of the support TiO₂ and platinum precursor significantly influenced the CO catalytic oxidation activity of platinum. X-ray diffraction, transmission electron microscopy, <i>in situ</i> diffuse reflectance infrared Fourier transform spectroscopy, and X-ray absorption fine structure analysis of the Pt/TiO₂ catalysts were carried out to correlate the relationship between the state of platinum and CO catalysis activity. The dispersion of Pt on different TiO₂ surfaces using diammine dinitritoplatinum as precursor decreased in the following order: Pt/rutile TiO₂ (rutile phase TiO₂ synthesized by hydrothermal method), Pt/anatase TiO₂ (by sol–gel method), and Pt/rutile TiO₂ (by sol–gel method). CO catalysis activity of Pt supported on different TiO₂ decreased with the decrease of Pt dispersion. Chloroplatinic acid played an important role in the formation of electron-rich platinum with lower Pt–Pt and Pt–O coordination number on rutile TiO₂ (hydrothermal) surface compared to that using diammine dinitritoplatinum as a metal salt precursor, which contributed to the highest CO catalysis oxidation activity

Unlock the Visible-Light Photocatalytic OWS by Surface Disorder-Engineered Bi-Based Composite Oxides through Phosphorization

It has been proven that the introduction of disorder in the surface layers can narrow the energy band gap of semiconductors. Disordering the surface’s atomic arrangement is primarily achieved through hydrogenation reduction. In this work, we propose a new approach to achieve visible-light absorption through surface phosphorization, simultaneously raising the energy band structure. In particular, the surface phosphorization of BixY1–xVO4 was successfully prepared by annealing them with a small amount of NaH2PO2 under a N2 atmosphere. After this treatment, the obtained BixY1–xVO4 showed distinct absorption in visible light. The surface phosphorization treatment not only improves the photocatalytic activity of BixY1–xVO4 but also enables visible-light photocatalytic overall water splitting. Furthermore, we demonstrate that this surface phosphorization method is universal for Bi-based composite oxides

Plasma Catalytic Removal of Hexanal over Co–Mn Solid Solution: Effect of Preparation Method and Synergistic Reaction of Ozone

Removal of hexanal via a post-plasma catalysis system over a Co–Mn solid solution at ambient temperature and pressure was investigated in this study. Results showed that CoMn­(9/1) prepared by a citric acid method exhibited the best catalytic activity, which could be ascribed to the higher redox property. Moreover, the coprecipitation method was applied and improved CO₂ selectivity significantly, which could be due to smaller grain size, larger surface area, and higher oxygen storage capacity. The reaction pathway and intermediates were analyzed by in situ Fourier transfrom infrared spectroscopy. In addition, results indicated that the removal of hexanal included direct decomposition by plasma and further oxidation of intermediates on the catalyst surface. Furthermore, it could be inferred that the intermediates were further oxidized by the synergistic effect between active oxygen species and catalyst and that the utilization of ozone was the key point in the process

Effect of Surface Self-Heterojunction Existed in Bi_<i>x</i>Y_1–<i>x</i>VO₄ on Photocatalytic Overall Water Splitting

Bi_<i>x</i>Y_1–<i>x</i>VO₄ solid solution, with absorption edge about 410 nm, is a new visible light photocatalysts based on V with d⁰ electron configuration for overall water splitting. However, Bi_<i>x</i>Y_1–<i>x</i>VO₄ prepared by solid state reaction always shows low photocatalytic activity and bad repeatability. In this paper, diluted acid was introduced to modify the Bi_<i>x</i>Y_1–<i>x</i>VO₄ prepared by solid state reaction. The photocatalytic activity of Bi_<i>x</i>Y_1–<i>x</i>VO₄ can be increased nearly four times after diluted acid treatment. The apparent quantum efficiency for overall water splitting at 380 nm is 3.4%. The enhanced photocatalytic water splitting activity is mainly attributable to the disappearance of BiO_<i>y</i> clusters on the surface of Bi_<i>x</i>Y_1–<i>x</i>VO₄. The adverse effects for water splitting induced by BiO_<i>y</i> clusters is explained by a novel surface self-heterojunction built between BiO_<i>y</i> clusters and Bi_<i>x</i>Y_1–<i>x</i>VO₄. Without diluted acid treatment, BiO_<i>y</i> clusters on the surface could capture photogenerated electrons by this surface self-heterojunction, which is bad for water splitting due to its lower conduction band

[MoS₄]^2– Cluster Bridges in Co–Fe Layered Double Hydroxides for Mercury Uptake from S–Hg Mixed Flue Gas

[MoS₄]^2– clusters were bridged between CoFe layered double hydroxide (LDH) layers using the ion-exchange method. [MoS₄]^2–/CoFe-LDH showed excellent Hg⁰ removal performance under low and high concentrations of SO₂, highlighting the potential for such material in S–Hg mixed flue gas purification. The maximum mercury capacity was as high as 16.39 mg/g. The structure and physical-chemical properties of [MoS₄]^2–/CoFe-LDH composites were characterized with FT-IR, XRD, TEM&SEM, XPS, and H₂-TPR. [MoS₄]^2– clusters intercalated into the CoFe-LDH layered sheets; then, we enlarged the layer-to-layer spacing (from 0.622 to 0.880 nm) and enlarged the surface area (from 41.4 m²/g to 112.1 m²/g) of the composite. During the adsorption process, the interlayer [MoS₄]^2– cluster was the primary active site for mercury uptake. The adsorbed mercury existed as HgS on the material surface. The absence of active oxygen results in a composite with high sulfur resistance. Due to its high efficiency and SO₂ resistance, [MoS₄]^2–/CoFe-LDH is a promising adsorbent for mercury uptake from S–Hg mixed flue gas

Trifunctional C@MnO Catalyst for Enhanced Stable Simultaneously Catalytic Removal of Formaldehyde and Ozone

The key challenge for controlling low concentration volatile organic compounds (VOCs) is to develop technology capable of operating under mild conditions in a cost-effective manner. Meanwhile, ozone (O₃) is another dangerous air pollutant and byproducts of many emerging air quality control technologies, such as plasma and electrostatic precipitators. To address these multiple challenges, we report here a design strategy capable of achieving the following trifunctions (i.e., efficiently VOCs adsorption enrichment, ozone destruction, and stable VOCs degradation) from the synergistic effect of adsorption center encapsulation and catalytic active sites optimization using 2D manganese­(II) monoxide nanosheets decorated carbon spheres with hierarchical core–shell structure. Carbonous residues in the as-synthesized MnO_<i>x</i> matrices played a key role for in situ generating homogeneous dispersed unsaturated MnO during the annealing of the as-synthesized C@MnO_<i>x</i> in the flow of argon under a proper calcination temperature (550 °C). The formation of the intimacy interface between MnO and carbon not only facilitates the adsorption and subsequent catalytic reaction but also results in a gatekeeper effect on the protection of the carbon sphere against the etching of O₃. Such a composite architecture achieved the highest stable removal efficiency (100% for 60 ppm of formaldehyde and 180 ppm of O₃ simultaneously) and 100% CO₂ selectivity under a GHSV of 60000 mL h^–1 g^–1. These findings thus open up a way to address current multiple challenges in air quality control using a single hierarchical core–shell structure