Ferroelectric-enhanced BiVO4-BiFeO3 photoelectrocatalysis for efficient, stable and large-current-density oxygen evolution

Abstract

The efficient BiVO4 photoanodes converting light to charge carriers and further oxidizing water to oxygen in PEC system is the gordian technical barrier for water spliltting, because that BiVO4 remain suffering from sluggish water oxidation kinetic, severe surface recombination and inefficient carrier separation. Firstly, the suitable cocatalysts loading can solve the sluggish kinetics of surface reaction and serious recombination of photogenerated charge carriers. Secondly, constructing heterostructures composed of multi-semiconductors can improve the separation efficiency of charge carriers and light absorption range. On the other hand, the existence of the built-in electric field can also provide a driving force for the transport of photoinduced charge carriers, thus enhancing separation efficiency. Herein, a ferroelectric enhanced photoelectrocatalysis system, by taking BiVO4 and Co3O4 as photocatalyst and cocatalyst, and coupling the ferroelectric material BiFeO3 to form BiVO4-BiFeO3 heterojunction was developed. The Co3O4 cocatalyst provided active sites for OER and BiVO4-BiFeO3 heterojunction promoted carrier separation. Besides of the regulation of heterojunction structure, BiFeO3 could also form the local internal electric field through ferroelectric polarization at a low voltage, which further promoted carrier separation and increased photocurrent. The as-prepared Co3O4/BiVO4-BiFeO3 sample exhibited remarkable electrocatalytic and photoelectrochemical activity for OER in 1 M KOH, an impressive photocurrent density at 1.23 V vs. RHE was achieved under AM 1.5 G light (2.24 mA/cm2), which was approximately double higher than those of Co3O4/BiVO4 and Co3O4/BiFeO3, respectively. Importantly, after the ferroelectric polarization of BiFeO3 was performed, photocurrent densities of 4.51 mA/cm2 at 1.23 V and 1280 mA/cm2 at 1.86 V vs. RHE were obtained under AM 1.5 G light, attesting the polarization-induced electric field contributed to enhance photoelectrochemical catalytic performance. The large-current-density OER obtained was also an important preponderance for the practicability.