In1–xGaxBO3 (0 ≤ x ≤ 0.5) – Solvothermal Synthesis, Morphology, and Performance in Photocatalytic Water Reduction

Partial solid solutions of In1–xGaxBO3 (0 ≤ x ≤ 0.5) were synthesized by the solvothermal method, and they were characterized by powder X‐ray diffraction, scanning and transmission electron microscopy, UV/Vis absorption spectroscopy, and N2 adsorption–desorption, in order to identify the phase purity and micromorphology. Nanocrystallites of InBO3 exhibit a particular anisotropic growth along the [110] direction, forming spindlelike morphology (with a diameter of ca. 20 nm and a length of ca. 200 nm). These nanocrystallites further aggregate into microspheres. With Ga3+ substitution, the anisotropic growth was depressed; the nanocrystallites thus exhibited a typical rodlike morphology. Metal borates are well‐known optical materials; however, their photocatalytic properties have been rarely studied. Here, post‐annealing under O2 flow at 350 °C improved the photocatalytic H2 evolution rate of InBO3 from 18.2(6) to 29.5(8) µmol h–1 g–1. A loading of Pt, RuOx, or NiOx as cocatalyst resulted in further enhancement of the H2 evolution rate, with an optimal value of 56.1(5) µmol h–1 g–1 under UV light. The solvothermal method was used to prepare partial solid solutions of In1–xGaxBO3 (0 ≤ x ≤ 0.5), in which InBO3 exhibits spindlelike nanocrystallites with the optimal photocatalytic H2 evolution rate of 56.1(5) µmol h–1 g–1 at a NiOx loading of 1 wt.‐%).