Photocatalytic Dehalogenation of Aromatic Halides on Ta2O5‑Supported Pt–Pd Bimetallic Alloy Nanoparticles Activated by Visible Light

• Published in: ACS catalysis Vol. 7; no. 8; pp. 5194 - 5201
• Main Authors: Sakamoto, Hirokatsu, Imai, Jun, Shiraishi, Yasuhiro, Tanaka, Shunsuke, Ichikawa, Satoshi, Hirai, Takayuki
• Format: Journal Article
• Language: English
• Published: American Chemical Society 04-08-2017
• Subjects: hot electron; alloy nanoparticle; visible light; photocatalysis; dehalogenation
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.7b01735

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 Ta2O5 (PtPd/Ta2O5), 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 (ehot –). They efficiently reduce the adsorbed H atoms and produce hydride species (H–) 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.