Black Gold-Based "Antenna-Reactor" To Activate Non-Plasmonic Nickel: Photocatalytic Hydrodechlorination and Hydrogenation Reactions

Activationof organic chlorides is a challenging reaction due totheir chemical inertness, while hydrogenation of alkene and alkynesfaces poor selectivity. In this work, we have demonstrated the useof nickel-loaded black gold (black Au-Ni) that absorbs broadbandlight from visible to near-infrared of the sunlight due to plasmoniccoupling between Au NPs, for photocatalytic hydrodechlorination andpropene and acetylene hydrogenation reactions. Hot carriers, the polarizingelectric field, and the photothermal effect generated in these catalystsenabled photocatalytic bond activation of these two challenging reactionsusing visible light at lower temperatures and atmospheric pressure.The black Au-Ni catalyst showed a multifold increase in itsactivity as compared to black Au. The plasmon-assisted reaction mechanismof hydrodechlorination was supported by intensity-dependent catalysis,kinetic isotope effect (KIE), competitive C-Cl bond activationwith one-electron ferricyanide reduction, finite-difference time-domain(FDTD) simulations, and quantum chemical studies. Cluster model-baseddensity functional theory studies show that the reactions have substantialbarriers, which were bypassed via an excited state accessed throughplasmonic excitations. FDTD studies indicate substantial enhancementof the electric field at the hotspots, iron reduction competed forhot carriers when run in conjunction with C-Cl bond activation,KIE was marginally higher in light as compared to the dark, and thecatalyst showed power-dependent activity. These observations indicatedthe hot carrier involvement in the hydrodechlorination reactions inaddition to the photothermal effect.