Hydrothermal Synthesis of Na_0.5La_0.5TiO₃–LaCrO₃ Solid-Solution Single-Crystal Nanocubes for Visible-Light-Driven Photocatalytic H₂ Evolution

摘要

Cubic perovskite structure photocatalysts of Na_0.5La_0.5TiO₃ and (Na_0.5La_0.5TiO₃)_1.00(LaCrO₃)_0.08 solid solution that consisted of well-defined single-crystal nanocubes were successfully prepared by means of facile and surfactant-free hydrothermal reactions for the first time. The results from different instrumental characterizations and theoretical calculations consistently confirmed the formation of nanocubic single-crystal solid solution of (Na_0.5La_0.5TiO₃)_1.00(LaCrO₃)_0.08, and clearly revealed the modification of its physicochemical properties compared with those of Na_0.5La_0.5TiO₃. In particular, the effective narrowing of the bandgap (from 3.19 to 2.25 eV) by Cr3+ in the solid solution made it possible to utilize visible light. The solid-solution configuration maintained the charge balance to preserve the valence of Cr3+ rather than Cr6+, and accommodated Cr3+ with high content to form new energy bands instead of localized impurity levels. The hydrothermal preparation strategy ensured the formation of single crystals with high purity, few defects, and regulated morphology; it also guaranteed the valences of Ti4+ and Cr3+ in the solid solution. Consequently, the recombination of photogenerated carriers could be effectively suppressed to benefit photocatalytic H₂ evolution. (Na_0.5La_0.5TiO₃)_1.00(LaCrO₃)_0.08 nanocubic single-crystal solid solution showed stable photocatalytic activity, and thus was proved to be a promising candidate for visible-light-driven photocatalytic H₂ evolution.