Effects of morphology and exposed facets of α-Fe2O3 nanocrystals on photocatalytic water oxidation

Shape and facet engineering of crystals at the nanoscale level has become an important strategy for optimizing the reactivity of catalysts in heterogeneous catalysis. We report here the fabrication of four morphology-controlled alpha-Fe2O3 catalysts with exposed specific facets by a solvothermal method. The effects of morphology and exposed facets of these alpha-Fe2O3 nanocrystals towards visible light-driven water oxidation have been investigated. Water oxidation was carried out using two catalytic systems, Fe2O3/[Ru(bpy)(3)](2+)/S2O82- and Fe2O3/AgNO3, at lambda > 420 nm. The alpha-Fe2O3 nanocubes with exposed {012} facets exhibit much higher catalytic activity than alpha-Fe2O3 nanoflakes with {001} facets. This work demonstrates that the catalytic activity of alpha-Fe2O3 nanocrystals in photocatalytic water oxidation is morphology-dependent and the reactivity trend can be rationalized in terms of exposed facets in the order of {012} > {001}. This study provides a new approach to the design of highly effective water oxidation catalysts by engineering the morphology and the exposed facets of crystals.