Pd/NiO core/shell nanoparticles on La_(0.02)Na_(0.98)TaO_3 catalyst for hydrogen evolution from water and aqueous methanol solution

摘要

Novel Pd/NiO core/shell nanoparticles (NPs) have been synthesized by a simple impregnation method with low temperature processing, in a 'green', scalable process using nontoxic chemicals. The cocatalyst consisting of a Pd core and a NiO shell formed simultaneously on the surface of La-doped NaTaO_3 photocatalyst. The Pd core both induces migration of photogenerated electrons from the bulk of the La_(0.02)Na_(0.98)TaO_3 and transfers electrons to the NiO shell. Without the NiO shell, Pd NPs show negligible H_2 production from water splitting, due to the rapid reaction between hydrogen and oxygen on the surface. On the other hand, the NiO shell allows the permeation of hydrogen and enables hydrogen reduction on Pd. The incorporation of NiO shell onto Pd remarkably enhances the photocatalytic performance of La-doped NaTaO_3 for hydrogen production from pure water. In addition, the core/shell structure can significantly enhance the stability of Pd during the photocatalytic reaction. Similar concepts could be extended to other applications, where the catalytic activity and stability are of concerns. The formation mechanism of the core/ shell photocatalyst is proposed based on the high resolution transmission electron microscopy (HRTEM) images and X-ray absorption near-edge structure (XANES) analyses.