Gold-Palladium Nanoalloys Supported by Graphene Oxide and Lamellar TiO2 for Direct Synthesis of Hydrogen Peroxide.

Abstract

Hybrid catalysts composed of gold-palladium nanoalloys that are sandwiched between layers of graphene oxide (GO) and lamellar TiO2 are synthesized via the deposition-reduction method. The resulting AuPd catalysts with different compositions of metal and support are fully characterized by a series of techniques, including X-ray diffraction, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry. The catalysts are also optimized against Au, Pd, GO, and TiO2 contents and employed in the direct synthesis of hydrogen peroxide (DSHP) from H2 and O2. The sandwich-like AuPd nanoalloy comprising 1 wt % nanoparticle of an equimolar mixture of Au and Pd with 6 wt % GO and 93 wt % TiO2 supports shows a promising catalytic performance toward the DSHP reaction with H2O2 productivity and selectivity of 5.50 mol H2O2 gmetal-1 h-1 and 64%, respectively. The catalyst is found to be considerably more active than those reported in the literature. Furthermore, the H2O2 selectivity of the catalyst is found to improve considerably to 88% when the TiO2 support is pretreated by HNO3. It is found that the perimeter sites of the interface of AuPd alloy and TiO2 are deemed as catalytically active sites for the DSHP reactions and the acidic property of TiO2 can retard the other overreactions and the decomposition of yielded H2O2. Results of the present study may provide a design strategy for partially covered catalysts that are confined by 2D materials for selective reactions.