An urchin-like Ag3PO4/Pd/LaPO4 photocatalyst with Z-scheme heterojunction for enhanced hydrogen evolution

An urchin-like LaPO₄-based nanocomposite integrating Ag₃PO₄ and Pd has been initially synthesized via a controllable self-assembly route, with enhanced photocatalysis and ultrastable structure for the synergistic hydrogen (H₂) evolution under sunlight. Citric acid was employed as a structure-mediated agent to guide the oriented growth of LaPO₄ along [101] facet at room temperature, showing the urchin-like 3D structure. Furthermore, Pd and Ag₃PO₄ were coated in turn resulting in the Ag₃PO₄/Pd/LaPO₄ nanocomposite, in which Pd and Ag₃PO₄ could act as the functions of electron receptor and electron donor in the photocatalysis, respectively. It was discovered that the as-developed nanocomposite could present the robust photocatalysis and stable morphology after consecutive uses. Based on the band structure analysis, a Z-scheme system of Ag₃PO₄/Pd/LaPO₄ was thereby proposed for the sunlight photocatalysis, as testified by DMPO spin trapping ESR spectra. Also, the photoluminescence and electrochemical impedance of nanocomposites were conducted, indicating that the improved carriers properties should be responsible mainly for the dramatically enhanced photocatalytic activities. Moreover, the outstanding photocatalytic performances of Ag₃PO₄/Pd/LaPO₄ were demonstrated in H₂ evolution (1084.3 μmol·g⁻¹·h⁻¹) under sunlight. Importantly, such a citric acid-controlled self-assembly route may pave the way toward the fabrication of multi-component photocatalyst tailored for the wide photocatalytic applications.