Thesing, Anderson, Loguercio, Lara F., Vaz, Maurício O., Khattak, Muhammad R. K., Franciosi, Gabriel, Lieberknecht, Gabriela, Castegnaro, Marcus V., Balzaretti, Naira M., Santos, Marcos J. L., and Santos, Jacqueline F. L.
The surface composition and organization of semiconductors play crucial roles in the efficiency of catalytic reactions, allowing for the tuning of optoelectronic properties and the prevention of charge recombination. Herein, we demonstrate a simple method to control the density of oxygen vacancies on hierarchical flower-like nanostructures of SrTiO3, prepared via a solvothermal reaction followed by heat treatment in an argon atmosphere. The morphological features from high-resolution transmission electron microscopy (HRTEM) revealed a disordered layer on the surface of the nanoparticles. Combined X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) analysis showed modifications in both occupied and unoccupied electronic states for the samples prepared at different temperatures, indicating that thermal treatment conditions effectively tune the electronic properties. In a cocatalyst-free approach, the maximum efficiency was achieved after heating the samples at 500 °C, reaching a hydrogen evolution rate of 8.78 μmol h–1, which is ca. 11 times higher than the sample thermally treated at 1000 °C in air. This improvement is primarily attributed to the interplay among structure, morphology, optical properties, and surface composition, minimizing losses by recombination. This work contributes to a better understanding of how to tune optoelectronic properties through surface modifications while controlling the morphological aspects of nanostructures, which is fundamental for synthesizing metal oxide materials with tailored properties.