Enhanced photoelectrochemical performance in BiVO4 photoanode by inserting the BiFeO3 ferroelectric thin layer

Abstract

Photoelectrochemical(PEC) water splitting is a promising method to generate hydrogen without any pollution. Among many photoelectrode materials, BiVO4(BVO) has received a lot of attention especially due to its theoretically high photocurrent density and moderate band gap. However, limitations such as rapid charge recombination and slow kinetics of the oxygen evolution reaction hinder their applications to PEC water splitting. Heterostructure with ferroelectric material could overcome these limitations, by allowing surface charges to assist charge separation and transfer. Herein, we successfully fabricated BVO/BiFeO3 (BFO) photoanodes on SrTiO3 (STO) substrate with bottom electrode SrRuO3 (SRO) via pulsed laser deposition. BFO is a well-known multiferroic material showing polarization of about 90 μCcm-2. We especially deposited BFO layers epitaxially to induce the self-polarization from epitaxial strain between BFO thin film and STO (001) substrate. Consequently, BVO/BFO photoanode showed a photocurrent density of 0.65 mA/cm-2 at 1.23 VRHE, which improved more than 3.5 times higher compared to the bare BVO/SRO photoanode. This improvement in PEC performance would be a result of favorable energy band modification due to upward self-polarized BFO surface charges, leading to suppression of charge recombination and efficient charge transfer.