Strain engineering of epitaxial perovskite-type LaFeO3/ BiFeO3 heterostructures for photoelectrochemical water splitting

Abstract

Following the approach of inducing structural constrains for the creation of polar nanodomains/nanoregions in the perovskite thin films, the photoelectrochemical properties of complex heterostructures based on LaFeO₃ and BiFeO₃ materials have been studied in correlation with the imposed structural strain and polarization orientation anisotropy conditions. The LFO/BFO thin film heterostructures have been tested using photoelectrochemical (PEC) technique. The recorded photocurrent values for the heterostructure with the LFO layer on top- LFO/BFO/STON- in the potentiodinamic regime are considerably higher (∼ 1.64 mA/cm² at 2 V vs RHE) than those obtained for BFO/LFO/STON heterostructure where the BFO layer is acting as the surface layer (∼ 0.32 mA/cm² at 2 V vs RHE). Moreover, the LFO/BFO/STON heterostructure exhibits both photocathodic and photoanodic behavior. The atomic resolution STEM data demonstrate the polarization orientation anisotropy in LFO/BFO/STON heterostructure, due to the cooperative effects of competing surface chemistry and polarization of the LFO/BFO interface over the magnitude and orientation of the Fe³⁺ cations displacement within the La³⁺ cages. For the BFO/LFO/STON heterostructure however, robust single-oriented domains with large Fe³⁺ cations displacement characteristics for long-range ferroelectric order, has been revealed also. Taking into account the possibility to control the PEC features such as charge distribution/transport characteristics for both photocathodic/photoanodic reactions, as well as the control of the polarization direction without a pre-poling process, this work is of relevance for applications where the use of a top electrode is not possible.