Construction of a Novel Cascade Electrolysis-Heterocatalysis System by Using Zeolite-Encaged Ultrasmall Palladium Catalysts for H 2 O 2 Generation.

In situ generation of hydrogen peroxide (H 2 O 2 ) has attracted extensive attention, especially in water treatment. However, traditional anthraquinones can only produce high-concentration H 2 O 2 and its transportation and storage are not convenient and dangerous. Herein, an in situ and on-demand strategy to produce H 2 O 2 by using a cascade water electrolysis together with a heterocatalysis system is provided. Beginning with water, H 2, and O 2 can be generated via electrolysis and then react with each other to produce H 2 O 2 immediately on efficient zeolite-encaged ultrasmall Pd catalysts. Significantly, the H 2 O 2 generation rate in the optimized cascade system reaches up to 0.85 mol L -1 h -1 g Pd -1 , overcoming most of the state-of-the-art catalysts in previous literature. The confinement effect of zeolites is not only beneficial to the formation of highly dispersed metal species, promoting the H 2 O 2 generation, but also inhibits the H 2 O 2 decomposition, enhancing the production yield of H 2 O 2 . In addition, the effect of electrolytes, sizes of Pd species, as well as zeolite acidity are also systematically studied. This work provides a new avenue for H 2 O 2 generation via a highly efficient cascade electrolysis-heterocatalysis system by using zeolite-supported metal catalysts. The high catalytic efficiency and green process for H 2 O 2 generation make it very promising for further practical applications.