Catalytically Active Oxidized PtOx Species on SnO<sub>2</sub> Supports Synthesized via Anion Exchange Reaction for 4-Nitrophenol Reduction
An anion exchange-assisted technique was used for the synthesis of platinum-decorated SnO<sub>2</sub> supports, providing nanocatalysts with enhanced activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). In this study, a series of SnO<sub>2</sub> support...
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| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Nanomaterials |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2079-4991/15/15/1159 |
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| Summary: | An anion exchange-assisted technique was used for the synthesis of platinum-decorated SnO<sub>2</sub> supports, providing nanocatalysts with enhanced activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). In this study, a series of SnO<sub>2</sub> supports, namely SnA (synthesized almost at room temperature), SnB (hydrothermally treated at 180 °C), and SnC (annealed at 600 °C), are systematically investigated, all loaded with 1 mol% Pt from H<sub>2</sub>PtCl<sub>6</sub> under identical mild conditions. The chloride ions from the SnCl<sub>4</sub> precursors were efficiently removed via a strong-base anion exchange reaction, resulting in highly dispersed, crystalline ~5 nm cassiterite SnO<sub>2</sub> particles. All Pt/SnO<sub>2</sub> composites displayed mesoporous structures with type IVa isotherms and H<sub>2</sub>-type hysteresis, with SP1a (Pt on SnA) exhibiting the largest surface area (122.6 m<sup>2</sup>/g) and the smallest pores (~3.5 nm). STEM-HAADF imaging revealed well-dispersed PtOx domains (~0.85 nm), while XPS confirmed the dominant Pt<sup>4+</sup> and Pt<sup>2+</sup> species, with ~25% Pt<sup>0</sup> likely resulting from photoreduction and/or interactions with Sn–OH surface groups. Raman spectroscopy revealed three new bands (260–360 cm<sup>−1</sup>) that were clearly visible in the sample with 10 mol% Pt and were due to the vibrational modes of the PtOx species and Pt-Cl bonds introduced due the addition and hydrolysis of H<sub>2</sub>PtCl<sub>6</sub> precursor. TGA/DSC analysis revealed the highest mass loss for SP1a (~7.3%), confirming the strong hydration of the PtOx domains. Despite the predominance of oxidized PtOx species, SP1a exhibited the highest catalytic activity (<i>k</i><sub>app</sub> = 1.27 × 10<sup>−2</sup> s<sup>−1</sup>) and retained 84.5% activity for the reduction of 4-NP to 4-AP after 10 cycles. This chloride-free low-temperature synthesis route offers a promising and generalizable strategy for the preparation of noble metal-based nanocatalysts on oxide supports with high catalytic activity and reusability. |
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| ISSN: | 2079-4991 |