Triple Play of Band Gap, Interband, and Plasmonic Excitations for Enhanced Catalytic Activity in Pd/HMoO Nanoparticles in the Visible Region.

Plasmonic photocatalysis has been limited by the high cost and scalability of plasmonic materials, such as Ag and Au. By focusing on earth-abundant photocatalyst/plasmonic materials (HMoO) and Pd as a catalyst, we addressed these challenges by developing a solventless mechanochemical synthesis of Pd/HMoO and optimizing photocatalytic activities in the visible range. We investigated the effect of HMoO band gap excitation (at 427 nm), Pd interband transitions (at 427 nm), and HMoO localized surface plasmon resonance (LSPR) excitation (at 640 nm) over photocatalytic activities toward the hydrogen evolution and phenylacetylene hydrogenation as model reactions. Although both excitation wavelengths led to comparable photoenhancements, a 110% increase was achieved under dual excitation conditions (427 + 640 nm). This was assigned to a synergistic effect of optical excitations that optimized the generation of energetic electrons at the catalytic sites. These results are important for the development of visible-light photocatalysts based on earth-abundant components.