Efficient solid-state synthesis of biomineralized vaterite-derived pure CaMnO3 perovskite for effective photocatalysis

Abstract

In recent years, perovskite materials have gained immense popularity due to their role in energy-based applications. Calcium manganese oxides are analogous to the systems that perform water-splitting in the natural photosynthesis process. In this work, we report a convenient method to synthesize CaMnO₃ perovskite. Biomineralized vaterite was used as the calcium source to synthesize pure CaMnO₃ efficiently. In contrast, commercial CaCO₃, which contains the calcite phase, led to the formation of a mixture of calcium manganese oxides. The low bandgap energy of pure CaMnO₃ (1.21 eV) enabled it to absorb visible light and be employed as a photocatalyst in the photolytic degradation of toxic dyes viz. rhodamine 6G, rhodamine B, methylene blue and methyl orange. The photocatalytic degradation of rhodamine 6G was studied in detail, and 72% dye degradation was observed within 2 h in the presence of pure CaMnO₃ in contrast to 46% in the presence of the mixed-phase calcium manganese oxide. The mechanistic pathway of dye degradation was also analysed.