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Simple temperature-regulated chemical vapor deposition was used to disperse iron oxide nanoparticles on porous Al 2 O 3 to create an Fe-oxide/Al 2 O 3 structure for catalytic NH 3 oxidation. The Fe-oxide/Al 2 O 3 achieved nearly 100% removal of NH 3 , with N 2 as a major reaction product at temperatures above 400 °C and negligible NO x emissions at all experimental temperatures. The results of a combination of in situ diffuse reflectance infrared Fourier-transform spectroscopy and near-ambient pressure-near-edge X-ray absorption fine structure spectroscopy suggest a N 2 H 4 -mediated oxidation mechanism of NH 3 to N 2 via the Mars-van Krevelen pathway on the Fe-oxide/Al 2 O 3 surface. As a catalytic adsorbent-an energy-efficient approach to reducing NH 3 levels in living environments via adsorption and thermal treatment of NH 3 -no harmful NO x emissions were produced during the thermal treatment of the NH 3 -adsorbed Fe-oxide/Al 2 O 3 surface, while NH 3 molecularly desorbed from the surface. A system with dual catalytic filters of Fe-oxide/Al 2 O 3 was designed to fully oxidize this desorbed NH 3 to N 2 in a clean and energy-efficient manner., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Au nanoparticles with a mean diameter of 20 nm with a coverage of ∼20% of the surface were distributed on a Si wafer surface and studied both before and after being annealed (at 100 and 300 °C). The two types of samples were analyzed using secondary ion mass spectroscopy (SIMS) with Bi 3 + clusters as the primary ions combined with surface etching using Ar 1000 + clusters. We observed a substantial difference in the SIMS spectra combined with a relatively short sputtering time of Ar 1000 + . In the nonannealed samples, bare Au cluster cations and Si + were observed in the SIMS spectra; AuSi + clusters were also observed in the annealed samples. These results indicate Au-silicide formation at a part of the periphery of the Au nanoparticles upon annealing. We suggest that SIMS experiments using cluster ions such as Bi 3 + can not only be used for surface elemental analyses but also provide information on local chemical environments of elements on the surface. This is an important issue in heterogeneous catalysis (e.g., strong metal-support interactions). We also advise that one should be careful interpreting the SIMS data combined with a longer Ar 1000 + sputtering time because this can deteriorate the surfaces from their original structures., Competing Interests: The authors declare no competing financial interest.

Mesoporous SiO 2 adsorbents were combined with Fe oxide nanoparticles (∼10 nm) that can catalyze thermal oxidation of organic compounds at low temperatures. Fe oxide nanoparticle (∼10 nm)-incorporated SiO 2 adsorbents were prepared via a temperature-regulated chemical vapor deposition method followed by a thermal annealing process. The removal efficiency and reusability of Fe oxide/SiO 2 particles were examined and compared to those of bare SiO 2 . Upon deposition of Fe oxide nanoparticles, not only the equilibrium adsorption capacity of mesoporous SiO 2 for methylene blue (MB) was improved but also the reusability of SiO 2 adsorbent was increased significantly. The adsorption ability of fresh Fe oxide/SiO 2 particles can be almost fully recovered by simple thermal annealing at atmospheric conditions (400 °C), whereas that of bare SiO 2 reduced significantly under same conditions. In addition, full recovery of initial MB adsorption ability of Fe oxide/SiO 2 can be achieved by a 100 °C annealing process. Fourier transform infrared, thermogravimetric analysis, and X-ray photoelectron spectroscopy analyses indicated that Fe oxide nanoparticles catalyzed thermal degradation of adsorbed MB molecules, resulting in the improved reusability of the Fe oxide/SiO 2 adsorbent. In addition to reusability, the equilibrium adsorption capacity of mesoporous SiO 2 particles for various cationic dye molecules, such as MB, malachite green, and rhodamine B, can be improved by combining Fe oxide nanoparticles., Competing Interests: The authors declare no competing financial interest.

Fe x O y H z nanostructures were incorporated into commercially available and highly porous alumina using the temperature-regulated chemical vapor deposition method with ferrocene as an Fe precursor and subsequent annealing. All processes were conducted under ambient pressure conditions without using any high-vacuum equipment. The entire internal micro- and mesopores of the Al 2 O 3 substrate with a bead diameter of ∼2 mm were evenly decorated with Fe x O y H z nanoparticles. The Fe x O y H z /Al 2 O 3 structures showed substantially high activity for acetaldehyde oxidation. Most importantly, Fe x O y H z /Al 2 O 3 with a high surface area (∼200 m 2 /g) and abundant mesopores was found to uptake a large amount of acetaldehyde at room temperature, and subsequent thermal regeneration of Fe x O y H z /Al 2 O 3 in air resulted in the emission of CO 2 with only a negligibly small amount of acetaldehyde because Fe x O y H z nanoparticles can catalyze total oxidation of adsorbed acetaldehyde during the thermal treatment. Increase in the humidity of the atmosphere decreased the amount of acetaldehyde adsorbed on the surface due to the competitive adsorption of acetaldehyde and water molecules, although the adsorptive removal of acetaldehyde and total oxidative regeneration were verified under a broad range of humidity conditions (0-70%). Combinatory use of room-temperature adsorption and catalytic oxidation of adsorbed volatile organic compounds using Fe x O y H z /Al 2 O 3 can be of potential application in indoor and outdoor pollution treatments., Competing Interests: The authors declare no competing financial interest.