Bulk Embedding of Ferroelectric Nanodomains in CuBi₂O₄ Photocathodes Enables Boosted Photoelectrochemical Hydrogen Generation

It is widely accepted that metal oxide-based photoelectrodes (MOPs) hold great promise for future solar hydrogen generation but are facing awkward challenge arising from their low intrinsic carrier mobility. The highly polarized nature of the predominantly ionic metal-oxygen bond always leads to the formation of small polarons that are responsible for the localized trapping of photo-generated carriers. Present study explores the reduction of carriers transport barrier via bulk embedding of ferroelectric nanodomains (FNDs) in MOPs that results in a new performance benchmark for the CuBi₂O₄ photocathode. By embedding laser-generated sub-10 nm BaTiO₃ nanocrystals in the bulk of CuBi₂O₄ photocathode, numerous FNDs are created that can lead to two times enhancement of the carrier mobility, which is proposed to originate from the overlaying of the internal electric fields and effective electrons transport channel at the heterointerfaces of BaTiO₃/CuBi₂O₄. Such strategy leads to the CuBi₂O₄ photocathode with the photocurrent density of up to 3.21 mA cm⁻² at 0.6 V_RHE, as well as a pronounced absorbed photon-to-current efficiency up to 80% at 400 nm. The universal feature of present technology is further verified by laser embedding of SrTiO₃ FNDs, providing an effective route for addressing the charge transport limitations in MOPs.