No abstract

Catalytic oxidation is believed to be the most efficient method for indoor formaldehyde purification. Herein, we reported that the Pt/Na-ZSM-5 catalyst with low Pt loading (0.16 wt %) prepared by depositing Pt on Na+ ion-exchanged ZSM-5 could completely oxidize 300 ppm formaldehyde in 2.5 vol % H2O at 32 °C and maintain its activity during the 62 h-long stability test. Multiple characterizations revealed that the presence of Na species significantly enhanced formaldehyde adsorption ability and made Pt species tend to exist in the form of metal Pt through electron transfer from Na to Pt, which promoted the activation of oxygen and opened a new efficient formaldehyde oxidation pathway, namely, direct decomposition of formate. The synergistic effects resulted in the TOF of Pt(0.16)/Na-ZSM-5 being about nine times higher than that of Pt(0.50)/ZSM-5. Our study showed that utilizing an alkali metal to tune the surface acidity/basicity of the support and the state of the supported noble metal was a promising way to improve the intrinsic catalytic performance and reduce noble metal usage.

Realizing the potential benefits of nanoscale metal catalysts requires highly dispersed active sites and control of their local environment. Herein, we develop a catalyst synthesis route for manipulating the local environment of highly dispersed metal-active sites via the targeted deposition of Pd near highly dispersed ZrO x on ZSM-5 zeolite using electrostatic interactions. The formed heteroatom Pd-ZrO x in zeolite catalysts is characterized by scanning transmission electron microscopy (STEM), in situ infrared spectroscopy, temperature-programmed desorption (TPD) of O 2 , and temperatureprogrammed surface reaction (TPSR) of CH 4 . The combination of diverse characterization results demonstrates the heteroatom Pd-ZrO x species rendering a higher dispersion and lower oxygen coordination of Pd species, appropriately tuning the strength of Pd−O bonds, and providing abundant active oxygen species to accelerate the dissociation of CH 4 . Therefore, the catalytic performance of Pd species is effectively enhanced with the lowest temperature of 90% CH 4 conversion decreasing from 390 °C (without ZrO x ) to 340 °C. Our work provides a strategy of engineering to anchor highly dispersed noble metal species and regulate the local environment to tune catalytic properties.