Enhanced Visible-Light H2O2 Production over Pt/g-C3N4 Schottky Junction Photocatalyst

Photocatalytic for hydrogen peroxide (H2O2) production is thought as a promising technology owing to its clean and green properties with the cheap and easily available raw materials of H2O and O2. Herein, Pt/g-C3N4 Schottky junction photocatalysts with ultralow Pt contents (0.025-0.1 wt %) were successfully fabricated by an impregnation-reduction method. It can efficiently reduce O2 to generate H2O2 without a sacrificial agent under visible-light irradiation. The yield of H2O2 produced over Pt0.05/g-C3N4 with the optimal 0.05 wt % Pt reached 31.82 μM, which was 2.46 times that of g-C3N4 and higher than most of those in the literature. It also showed good stability in three repeated tests. The deposition of highly dispersed metal Pt nanoparticles with low and limited content can expose enough active Pt atoms, significantly enhance the separation efficiency of photogenerated carriers, and reduce its negative effect on H2O2 decomposition, resulting in improved and outstanding efficiency of H2O2 production. The ·O2- radicals were found to be the main active species. The mechanism of photocatalytic H2O2 production was confirmed to be a two-step single electron route (O2 + e-→ ·O2- → H2O2).

One-step fabrication of electrospun flexible and hierarchically porous Pt/γ-Al2O3 nanofiber membranes for HCHO and particulate removal

A flexible Pt/γ-Al2O3 nanofiber membrane with optimal 2 wt% Pt content can effectively decompose HCHO into CO2 at room temperature.

Single Tungsten Atom-Modified Cotton Fabrics for Visible-Light-Driven Photocatalytic Degradation and Antibacterial Activity

Various single-atom materials exhibit distinguished performances in catalysis and biology. To boost their applications, single-atom-based strategies are highly demanded to exhibit repeatable functions on advanced wearable substrates. However, single-atom approaches are rarely reported to anchor on wearable materials, i.e., widely applied cotton fabrics. Here, we developed a simple method of loading uniformly dispersed single tungsten atoms on cotton via ordinary direct-dye processing to exhibit superior sustainable functions. The single sites of tungsten atom centers are constructed by binding oxygen-coordinated single tungsten atom on the cotton fabric surface via -COOH groups. Consequently, the band gap of single sites decreases significantly to 2.75 from 3.03 eV. Therefore, the single-site-modified cotton exhibits excellent visible-light-driven (>420 nm) photocatalytic degradation efficiency of organic dyes, which exceeds other reported cotton-based materials by nearly two orders of magnitude. Furthermore, the single-site-modified cotton also exhibits great antibacterial performance due to reactive oxygen species. Moreover, the cotton with anchored single sites possesses great washing-resistance ability during 20 laundry cycles under soap-washing conditions. After recycling, the single sites on cotton have no obvious changes in the microstructure, which demonstrates the success of our sustainable strategy of single sites anchored on cotton. The single-site technique can be extended to many other elemental atoms on various wearable devices, providing a playground for functional material communities.

Fabrication of Pd/CeO2 nanocubes as highly efficient catalysts for degradation of formaldehyde at room temperature

The highly active Pd/CeO2 nanocube interface guarantees a high percentage of metallic Pd and the surface active O species is responsible for the complete decomposition of formaldehyde.

Facet- and defect-engineered Pt/Fe2O3 nanocomposite catalyst for catalytic oxidation of airborne formaldehyde under ambient conditions

Formaldehyde (HCHO) is one of the most infamous indoor pollutants that imposes a great threat to human health. Herein, we report the development of a high-performance Pt/Fe₂O₃ catalyst for HCHO oxidation employing a facet- and defect-engineering strategy, with special focus on the surface structure effect of α-Fe₂O₃ on the catalytic properties. A supported Pt nanocatalyst on hollow octadecahedral α-Fe₂O₃ with exclusively exposed {113} and {104} facets was prepared using a hydrothermal method followed by impregnation-reduction treatment. The high-index facets of α-Fe₂O₃ render the formation of abundant oxygen vacancies and an improved dispersion of Pt nanoparticles. This led to an increased Pt/O-vacancy coexistence in close proximity, which collaboratively promote the generation of active oxygen and surface OH species. As a consequence, the Pt/Fe₂O₃-HO catalyst exhibited impressively high and stable activity towards HCHO oxidation at room temperature, which was five-fold higher than that of the supported Pt catalyst on commercial α-Fe₂O₃.

A TiO2/C catalyst having biomimetic channels and extremely low Pt loading for formaldehyde oxidation

This study presents a TiO2/C hybrid material with biomimetic channels fabricated using a wood template. Repeated impregnations of pretreated wood chips in a Ti precursor were conducted, followed by calcination at 400-600 °C for 4 hours under a nitrogen atmosphere. The generated TiO2 nanocrystals were homogenously distributed inside a porous carbon framework. With an extremely low Pt catalyst loading (0.04-0.1 wt%), the obtained porous catalyst could effectively oxidize formaldehyde to CO2 and H2O even under room temperature (conv. ∼100%). Wood acted as both a structural template and reduction agent for Pt catalyst generation in sintering. Therefore, no post H2 reduction treatment for catalyst activation was required. The hierarchal channel structures, including 2-10 nm mesopores and 20 μm diameter channels, could be controlled by calcination temperature and atmosphere, which was confirmed by SEM and BET characterizations. Based on the abundant availability of wood templates and reduced cost for low Pt loading, this preparation method shows great potential for large-scale applications.

Highly Efficient Performance and Conversion Pathway of Photocatalytic CH3SH Oxidation on Self-Stabilized Indirect Z-Scheme g-C3N4/I3--BiOI

A self-stabilized Z-scheme porous g-C₃N₄/I^3--containing BiOI ultrathin nanosheets (g-C₃N₄/I^3--BiOI) heterojunction photocatalyst with I₃^-/I^- redox mediator was successfully synthesized by a facile solvothermal method coupling with light illumination. The structure and optical properties of g-C₃N₄/I^3--BiOI composites were systematically characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, N₂ adsorption/desorption, UV-vis diffuse reflectance spectrum, and photoluminescence. The g-C₃N₄/I^3--BiOI composites, with a heterojunction between porous g-C₃N₄ and BiOI ultrathin nanosheets, were first applied for the photocatalytic elimination of ppm-leveled CH₃SH under light-emitting diode visible light illumination. The g-C₃N₄/I^3--BiOI heterojunction with 10% g-C₃N₄ showed a dramatically enhanced photocatalytic activity in the removal of CH₃SH compared with pure BiOI and g-C₃N₄ due to its effective interfacial charge transfer and separation. The adsorption and photocatalytic oxidation of CH₃SH over g-C₃N₄/I^3--BiOI were deeply explored by in situ diffuse reflectance infrared Fourier transform spectroscopy, and the intermediates and conversion pathways were elucidated and compared. Furthermore, on the basis of reactive species trapping, electron spin resonance and Mott-Schottky experiments, it was revealed that the responsible reactive species for catalytic CH₃SH composition were h⁺, ^•O₂^-, and ¹O₂; thus, the g-C₃N₄/I^3--BiOI heterojunction followed an indirect all-solid state Z-scheme charge-transfer mode with self-stabilized I₃^-/I^- pairs as redox mediator, which could accelerate the separation of photogenerated charge and enhance the redox reaction power of charged carriers simultaneously.

Active oxygen species adsorbed on the catalyst surface and its effect on formaldehyde oxidation over Pt/TiO2 catalysts at room temperature; role of the Pt valence state on this reaction?

Pt/TiO2 catalysts, prepared by reduction pretreatment, showed enhanced catalytic activities in formaldehyde oxidation. X-ray photoelectron spectroscopy analysis confirmed that catalytic activity was affected by Pt valence states in the Pt/TiO2 catalyst. Using O2 re-oxidation tests, we showed that there was a correlation between the area of oxygen consumed and the ratio of metallic Pt species on the catalyst surface. The O2 re-oxidation ability was involved in the production of the adsorbed formate intermediate from HCHO, confirmed through diffuse reflectance infrared Fourier transform spectroscopy analysis. Furthermore, metallic Pt species were involved in the oxidation of adsorbed CO to CO2.

Ag–K/MnO2 nanorods as highly efficient catalysts for formaldehyde oxidation at low temperature

A series of Ag–K/MnO₂ nanorods with various molar ratios of K/Ag were synthesized by a conventional wetness incipient impregnation method. The as-prepared catalysts were used for the catalytic oxidation of HCHO. The Ag–K/MnO₂ nanorods with an optimal K/Ag molar ratio of 0.9 demonstrated excellent HCHO conversion efficiency of 100% at a low temperature of 60 °C. The structures of the samples were investigated by BET, TEM, SEM, XRD, H₂-TPR, O₂-TPD and XPS. The results showed that Ag–0.9K/MnO₂-r exhibited more facile reducibility and greatly abundant surface active oxygen species, endowing it with the best catalytic activity of the studied catalysts. This work provides new insights into the development of low-cost and highly efficient catalysts for the removal of HCHO.

Ag–K/MnO₂ nanorods with appropriate K/Ag ratio demonstrated excellent catalytic activity for complete oxidation of formaldehyde.