Compositional Screening of the Pb–Bi–Mo–O System. Spontaneous Formation of a Composite of p‑PbMoO₄ and n‑Bi₂O₃ with Improved Photoelectrochemical Efficiency and Stability

Scanning electrochemical microscopy (SECM) was used to identify more efficient p-type photocatalysts for H⁺ reduction in the Pb–Bi–Mo trimetal oxide system. An atomic ratio of (1:1:1) between Pb, Bi, and Mo showed higher photocurrent than other spots in screening experiments. The crystal structure of Pb–Bi–Mo oxide was studied by X-ray diffraction, indicating that a composite of p-PbMoO₄ and n-Bi₂O₃ coexisted as a heterostructure. Photoelectrochemical performance of the p-PbMoO₄/n-Bi₂O₃ composite electrode showed enhanced stability for the H⁺ and O₂ reduction reactions. We propose a reaction mechanism to explain this stabilization of a p-type semiconductor.