Fabrication of robust M/Ag3PO4 (M = Pt, Pd, Au) Schottky-type heterostructures for improved visible-light photocatalysis

Abstract

M/Ag₃PO₄ (M = Pt, Pd, Au) Schottky-type heterostructures were successfully fabricated by a chemical deposition route using NaBH₄ as a reduction agent. The structure and optical properties of the as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and electrochemical techniques. The photocatalytic activity was evaluated by the decomposition of dyes (methyl orange, methylene blue, and rhodamine B) under visible light irradiation (λ > 420 nm). These noble metals as nanoparticles were highly dispersed on the surface of Ag₃PO₄ polyhedrons. The light absorption of Ag₃PO₄ in both the UV and visible regions was extensively increased upon noble metal deposition. The photocurrent response over M/Ag₃PO₄ electrodes was much higher than that of pure Ag₃PO₄ and followed the decreased order of Pt > Pd > Au. The metallic nanoparticles deposited on Ag₃PO₄ could promote the transfer of photo-generated electrons, which not only inhibited the recombination of electrons and holes effectively, but also suppressed the photocorrosion of Ag₃PO₄, leading to a significant increase in photocatalytic activity and stability. On the basis of radical-trapping experiments and the PL technique, h⁺ and ˙O₂⁻ were well-established to correspond to the quick photo-degradation of dyes and a possible mechanism was proposed.