Decorating geometry- and size-controlled sub-20 nm Pd nanocubes onto 2D TiO2 nanosheets for simultaneous H2 evolution and 1,1-diethoxyethane production

Abstract

The morphological characteristics of metal play a pivotal role in affecting the activity of metal–semiconductor composite photocatalysts for solar energy conversion. In this article, geometry- and size-controlled sub-20 nm Pd nanocubes (NCs) have been fabricated and hybridized with 2D TiO₂ nanosheets (TNS) to explore how the geometry and size of Pd influences the photocatalytic efficiency of Pd-based semiconductor composites. The photoactivity results evaluated by the dual-function photocatalytic system for simultaneous H₂ evolution and 1,1-diethoxyethane (DEE) production suggest that Pd NCs endow TNS with a greatly enhanced photoactivity compared to Pd nanoparticles (NPs) supported on 2D TNS. The activation energy for H₂ generation and the adsorption affinity between Pd and hydrogen molecules can be modulated by the geometry differences between Pd NCs and Pd NPs. Meanwhile, the activity of TNS–Pd NCs composites can be increased by decreasing the size of the Pd NCs from 17 to 7 nm, which is predominantly attributed to the more efficient capability of small Pd NCs to boost the separation and transportation of photoexcited electron–hole pairs. Our work not only fundamentally elucidates the relationship between the morphological characteristics of metal Pd and the photoactivity of Pd-based semiconductor composites, but also supplies a dual-purpose sustainable way for simultaneous H₂ evolution and organic synthesis of fine chemicals.