Position of Gold Dictates the Photophysical and Photocatalytic Properties of Cu2O in Cu2O/Au Multicomponent Nanoparticles

Utilizing solar radiation for driving chemical reactions has been of great interest in the last decade. Although Cu2O nanocrystals as a low-cost, abundant, and tailorable photocatalyst are promising candidates to provide a platform for solar-driven applications, their photophysical properties are affected by the limited charge carrier mobility. This paper focuses on the more efficient utilization of the UV light-excited charge carriers in cuprous oxide by preparing different heterostructures with gold. While keeping the size, shape as well as overall composition of the heterostructures identical, the realization of the gold component is varied: either nanograins are created at the surface of the Cu2O nanooctahedra or nanorods are embedded in their interior. The effect of the morphology and the semiconductor-metal contact on the optical and photocatalytic properties is investigated in-detail by spectroscopy, spectrofluorometry, imaging techniques, X-ray diffractometry, and photoelectron spectroscopy extended with optical simulations and single-particle spectroscopy measurements. In terms of particle stability and photocatalytic activity, gold-decorated Cu2O nanooctahedra show superior properties. The comprehensive comparison of the multicomponent nanoparticles underlines the importance of the nanoscale design (including composition, morphology, and surface chemistry), which utilizes the photoexcited carriers in the semiconductor without injecting hot electrons from the metal.