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

Abstract 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 CuBi 2 O 4 photocathode. By embedding laser‐generated sub‐10 nm BaTiO 3 nanocrystals in the bulk of CuBi 2 O 4 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 BaTiO 3 /CuBi 2 O 4 . Such strategy leads to the CuBi 2 O 4 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 SrTiO 3 FNDs, providing an effective route for addressing the charge transport limitations in MOPs.