The construction of Ru-doped In2O3 hollow peanut-like structure for an enhanced photocatalytic nitrogen reduction under solar light irradiation

Abstract

The synthesis of metal–organic framework (MOF) materials has been considered as an effective strategy for the design and fabrication of various nanostructured metal-based functional photocatalysts recently. Herein, Ru-doped In₂O₃ hollow peanuts (denoted as Ru–In₂O₃ HPNs) derived from MIL-68-In(Ru) precursor calcined in air was employed as an efficient photocatalytic system for the photoreduction of nitrogen. The TEM images revealed the uniform distribution of In₂O₃ nanoparticles, which are in situ-assembled to form a hollow peanut structure. Accordingly, this tailored nanostructure facilitates the separation and transportation of photoinduced electron–hole pairs and favor light harvesting by multi-reflection/scattering. Moreover, Ru dopants are intentionally introduced into the In₂O₃ semiconductor as active sites, which not only narrows the bandgap energy but also causes the formation of abundant oxygen vacancies (OVs), promoting the photocatalytic reduction reaction. As a result, the unique structure of Ru–In₂O₃ exhibited the highest photocatalytic activity of 44.5 μmol g⁻¹ h⁻¹ for ammonia production under solar-light irradiation, which is 5.7-times and much higher than that of pure In₂O₃ hollow peanuts and bulk In₂O₃, respectively. Further, Ru–In₂O₃ HPNs exhibited excellent stability for photocatalytic nitrogen fixation by showing no obvious activity decay for six consecutive two-hour tests (12 h). This work might open up some insights into the target-directed design of hollow materials for the photocatalytic nitrogen fixation.