Reversible hydrogen spillover induced by Brønsted acid for accelerating direct synthesis of hydrogen peroxide

Abstract

Supported PdAu bimetallic nanoparticles have been developed for the direct synthesis of H2O2 (DSHP). However, to date, the dilute H2 streams necessary to avoid potential risks of explosion limits the attainable product concentrations of H2O2. Here, a series of silicon-modified Al2O3 (SixAl) were synthesized for loading PdAu bimetallic nanoparticles. The H2 consumption turnover frequency (TOF) and H2O2 formation TOF show a volcano trend with the silica content, where PdAu/Si5.6Al exhibits the best H2 consumption TOF and H2O2 formation TOF (11259.3 and 1995.2 h−1). Silica on the surface of Al2O3 is identified as Brønsted (B) acid site. The increase of B acid sites density accelerates the H2 conversion into H atoms, thereby boosting H2O2 formation process. The adsorption and dissociation of H2 into atomic H at B acid sites would spill across the support to PdAu nanoparticles reversely. The reversed hydrogen spillover effect induced by B acid site accounts for enhanced H2 conversion and H2O2 productivity for PdAu/SixAl.