Plasmon Enhanced Nickel(II) Catalyst for Photocatalytic Lignin Model Cleavage

Photocatalytic-induced cleaving of the ether C–O bond in model lignin compounds was studied with a closely-coupled compo-site material consisting of Ni(OH)₂ and gold nanoparticles (NPs) on a zirconia support (Au/ZrO₂–Ni(OH)₂). The three important ether bond types consisting of α-O-4, β-O-4, and 4-O-5 linkages can all be cleaved using this catalyst at reaction temperatures 40, 85 and 95 °C when under low-flux visible light irradiation. The Au NPs action as a light-harvesting antenna provided light-generated hot electrons that reduced Ni²⁺ to Ni⁰. The Ni⁰ was the active catalytic site where reductive cleavage of ether C–O bonds occurred while it was oxidized to Ni²⁺ to complete the catalysis cycle. The plasmonic antenna system with supported Ni(OH)₂ exhibited better ability for the catalytic reductive ether cleavages under visible light irradiation compared to photocata-lysts of Au NPs and Ni²⁺ ions immobilized on alumina fibers.