Photocatalytic Dehalogenation of Aromatic Halides
on Ta<sub>2</sub>O<sub>5</sub>‑Supported Pt–Pd Bimetallic
Alloy Nanoparticles Activated by Visible Light
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Abstract
Dehalogenation
of aromatic halides is one important reaction for
detoxification and organic synthesis. Photocatalytic dehalogenation
with alcohol, a safe hydrogen source, is one promising method; however,
systems reported earlier need UV irradiation. We found that Pt–Pd
bimetallic alloy nanoparticles (ca. 4 nm) supported on Ta<sub>2</sub>O<sub>5</sub> (PtPd/Ta<sub>2</sub>O<sub>5</sub>), on absorption of
visible light (λ > 450 nm), efficiently promote dehalogenation
with 2-PrOH as a hydrogen source. Catalytic dehydrogenation of 2-PrOH
on the alloy in the dark produces hydrogen atoms (H) on the particles.
Photoexcitation of d electrons on the alloy particles by absorbing
visible light produces hot electrons (e<sub>hot</sub><sup>–</sup>). They efficiently reduce the adsorbed H atoms and produce hydride
species (H<sup>–</sup>) active for dehalogenation. The catalytic
activity depends on the Pt/Pd mole ratio; alloy particles consisting
of 70 mol % of Pt and 30 mol % of Pd exhibit the highest activity
for dehalogenation
