Flame spray pyrolysis engineering of nanosized mullite-bi2fe4o9 and perovskite-bifeo3 as highly efficient photocatalysts for o2 production from h2o splitting

Abstract

Bi-Fe oxides are stable materials with potential photocatalytic activity under solar light photons. So far, however the photocatalytic potential of pure-phase nanosized mullite-Bi2Fe4O9 has not been studied. Usually, synthesis of pure-phase nanosized mullite-Bi2Fe4O9 is hampered by co-formation with perovskite BiFeO3 . Herein we demonstrate that pure-phase mullite-Bi2Fe4O9 nanoparticles prepared by Flame Spray Pyrolysis (FSP) technology are highly efficient O2 production photocatalysts, achieving >1500 µmol g−1h−1 . This outperforms all-so far reported-O2 production Bi-Fe-O photocatalysts. We present an FSP-based process for production of a versatile Bi-Fe-O platform, that can be easily optimized to obtain 100% mullite-Bi2Fe4O9 or 100% perovskite-BiFeO3 or their heterojunctions. The phase-evolution of the Bi-Fe-O materials has been studied by XPS, Raman, and EPR spectroscopies. Short post-FSP annealing process impacts the photoactivity of the BiFeO3 and Bi2Fe4O9 in distinct ways. Fe2+ centers in BiFeO3 can improve dramatically its O2 production efficiency, while solid-melt formation in Bi2Fe4O9 is a limiting factor.