Zhanming Chen

Supported Pt catalysts are highly active for the selective catalytic oxidation of ammonia (NH₃-SCO), but their practical use is limited by poor N₂ selectivity and insufficient hydrothermal durability under high-temperature exhaust conditions. Herein, we report a composition-regulated high-entropy oxide interface strategy to stabilize Pt–Cu dual sites and steer NH₃ oxidation toward selective N₂ formation. A series of fluorite-type Ce-based high-entropy oxides, including CeZrLaPrYO_x, CeSmLaPrYO_x, and CeSnLaPrYO_x, were constructed as thermally robust supports for Pt and Cu loading. Among them, PtCu/HEO-Zr calcined at 1000 °C exhibits the best NH₃-SCO performance, achieving 90% NH₃ conversion at 260 °C while maintaining N₂ selectivity above 80% over a broad temperature window of 100–300 °C under a high weight hourly space velocity of 100,000 mL·g⁻¹·h⁻¹. More importantly, after harsh hydrothermal aging at 800 °C with 10 vol% H₂O for 12 h, the catalyst shows negligible activity loss and nearly unchanged N₂ selectivity, demonstrating exceptional structural and catalytic robustness. Structural and surface analyses reveal that Zr incorporation optimizes the fluorite high-entropy lattice, increases oxygen vacancy concentration, promotes lattice oxygen mobility, strengthens surface acidity, and enriches active Cu²⁺ species, thereby enhancing the interfacial cooperation between NH₃ activation and oxygen-assisted intermediate conversion. In situ DRIFTS further reveals that PtCu/HEO-Zr favors an O_lat-assisted internal selective catalytic reduction pathway, in which adsorbed NH₃ is activated to -NH₂ species and subsequently reacts with lattice oxygen-derived intermediates to form N₂O₂²⁻-like species that decompose into N₂ and H₂O. Meanwhile, the formation of nonselective NO_x and N₂O products is suppressed. This work highlights high-entropy oxide-supported Pt–Cu interfaces as a promising platform for designing hydrothermally durable and N₂-selective NH₃-SCO catalysts.

Methanol fuel engines can effectively reduce emissions of carbon monoxide and particulate matter, but they cause a substantial increase in emissions of unregulated pollutants like methanol and formaldehyde. In this study, Ag/CeO₂ catalysts were prepared from metal–organic framework (MOF) and silver acetate precursors using different methods and applied to the deep oxidation of methanol. The influence of preparation conditions on the types of active oxygen, surface chemical state, and oxygen vacancies was revealed by changing the calcination conditions and compared with the Ag/CeO₂ catalyst prepared by traditional methods. At the same time, the low-temperature reaction pathway of methanol was explored. The results showed that calcination conditions greatly affected the structure of the catalyst. Among them, Ag/CeO₂-A500 obtained by calcining Ag/Ce BTC in air at 500 °C had the best catalytic performance for methanol oxidation. The surface chemical state, overall oxygen vacancies, and the proportion of metallic silver may be key factors for its superior catalytic performance.

The spray characteristics of liquid ammonia under various ambient pressures and temperatures were analyzed in a constant volume chamber to cover a wide range of superheat degrees. The injection pressure was set as 70 and 80 MPa with ambient pressure ranging from 0.2 to 4 MPa. The ambient temperature was 500 K. The results showed that the higher the injection pressure, the greater the kinetic energy obtained. The droplet fragmentation was enhanced, and the phenomenon of gradual separation of the gas–liquid region occurred with increasing injection pressure. Under flash boiling spray conditions, the spray developed faster than non-flash boiling and transition flash boiling spray under the same injection pressure. In addition, the flash boiling spray tip penetration of the gas and liquid increased more than that of cold spray, and the fluctuation of the late stage of the injection was relatively large. Therefore, the injection pressure has a greater effect on the spray tip penetration of flash boiling spray. Moreover, ambient pressure greatly influences the flare flash boiling spray. The spray resistance phenomenon was found during the spray development in the flare flash boiling condition. With the increase in ambient pressure, the spray tip penetration of flash boiling spray decreases due to the reduction in the pressure difference inside and outside the spray hole and the restriction of ambient gas. Meanwhile, owing to the low ambient pressure and ambient density, the liquid penetration in the initial phase of the flare flash boiling spray will be abnormally shorter than that of the non-flash boiling spray.