A high surface area ordered mesoporous BiFeO3 semiconductor with efficient water oxidation activity

Abstract

Bismuth ferrite (BiFeO₃) is an important multiferroic oxide material because of its unique magnetic and ferroelectric properties. Here, we synthesize for the first time a highly ordered mesoporous BiFeO₃ semiconductor using tartaric acid-assisted growth of the BiFeO₃ compound inside the pores of a carbon template. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and N₂ physisorption measurements reveal that the template-free material possesses a three-dimensional hexagonal mesostructure with a large internal BET surface area (141 m² g⁻¹) and narrow sized pores (ca. 4 nm). Also, the pore walls comprise single-phase BiFeO₃ nanocrystals according to the high-resolution TEM, electron diffraction and magnetic experiments. The mesoporous BiFeO₃ shows high activity for the photocatalytic oxygen evolution reaction (OER) under UV-visible light (λ > 380 nm), affording an average oxygen evolution rate of 66 μmol h⁻¹ g⁻¹. We also show that the propensity of photogenerated holes for the OER can be significantly enhanced when 1 wt% Au nanoparticles are deposited on the BiFeO₃ surface. The Au/BiFeO₃ heterostructure exerts excellent OER activity (586 μmol h⁻¹ g⁻¹) and long-term cycling stability, raising the possibility for the design of effective and robust OER photocatalysts.