In recent years, bismuth-based photocatalysts have been receiving increasing attention in photocatalysis, due to their appropriate bandgap and tunable surface structure, which make them suitable also for the photocatalytic reduction of CO₂¹. Their performances, however, are still limited by the fast charge carriers recombination. Recently, the exploitation of piezo/ferro-electric potentials in photo-active semiconductors has been adopted as an effective strategy to modulate the charge transfer properties both in the bulk phase and at the surface of semiconductors (i.e. piezo-phototronic effect)². In this perspective Bismuth-based Aurivillius compounds, owing to their usually strong spontaneous ferroelectric polarization represent a promising option as cell photo-electrodes, allowing the increase of cell efficiency by electrically polarizing the materials. In addition, thanks to their unique layered structure, this peculiar class of perovskites allows the migration of photo-generated holes and electrons within different areas of the materials, thus intrinsically facilitating charge separation.

In this work, the utilization of different Aurivillius compounds (i.e. Bi₄Ti₃O₁₂ – BiTO, and Bi₂MoO₆ - BiMO) as photo-electrode materials for solar conversion has been studied in detail. The use of BiTO and BiMO for the photocatalytic reduction of CO₂ has recently been reported, however, the main strategies to develop optimized ferroelectric-enhanced photo-electrodes of these materials and their utilization for the ferroelectric potential-assisted CO₂ reduction has never been fully investigated. BiTO and BiMO photo-electrodes were fabricated and accurately optimized to obtain both hierarchically oriented nanostructures with different morphologies (i.e. nanosheet/nanorod arrays), and thin-film layers via in situ hydrothermal deposition and through a sol-gel/spin coating coupled process respectively. The effect of the ferroelectric potential on the photo-electrochemical performances of the optimized photo-electrodes with different architectures was therefore accurately studied. Density current increments and enhanced charge transfer ability were registered under the optimal ferroelectric polarization which was directly reflected in the CO₂ photo-electrochemical reduction performances. This work, therefore, demonstrates the possibility to adopt ferroelectric polarization coupled with an external bias to effectively control the migration of photo-generated charges in bismuth-based Aurivillius semiconductors for the CO₂ photo-electrochemical reduction.