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 g_metal^-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.