Enhanced Photocatalytic Efficiency of a Least Active Ag-TiO by Amine Adsorption.

An Ag-TiO photocatalyst with 3.5 atom % silver content, synthesized by a single step sol-gel method, possessed silver nanoparticles (AgNPs; 1-5 nm) on the TiO surface, but owing to the nonplasmonic nature of AgNPs and the wide band gap of TiO, this material exhibited poor activity in a photocatalytic degradation reaction. However, this least active Ag-TiO catalyst showed a sudden increase in activity during a photocatalytic amine self-coupling reaction showing the highest activity, which was interpreted as amine (reactant) adsorption-driven activity enhancement. We found that amine adsorption occurred over AgNPs converting into plasmonic AgNPs as well as on the TiO surface reducing the band gap and therefore facilitated the visible light excitation and the electron-transfer process efficiently, resulting into overall enhancement in the photocatalytic activity. Thus, a very efficient, stable, and visible light active photocatalyst (amine-adsorbed Ag-TiO) was developed by simply adsorbing an amine in the least active Ag-TiO photocatalyst.