Spontaneous polarization of ferroelectric heterostructured nanorod arrays for high-performance photoelectrochemical cathodic protection

Corrosion is a critical global problem for the steel industry and a grand challenge toward Net-Zero clean growth. TiO₂ nanorods (TNRs) have been developed for photoelectrochemical cathodic protection (PCP) of coupled metal. However, the performance was hindered by their wide bandgap, weak visible-light response, and low separation efficiency of photocarriers. In this work, a unique multilayered coaxial nanorod array (TNRs/BTO/Ag NPs) structure has been proposed to enhance ‘hot’ electrons injection via inserting a ferroelectric semiconductor BaTiO₃ (BTO) nanolayer between TNRs and Ag nanoparticles (Ag NPs). The spontaneous ferroelectric BTO nanolayer built a polar charge-induced electric field (PEF), resulting in a strong spontaneous polarization. Furthermore, the as-proposed structure can negatively shift the surface potential of the coupling 304 stainless steel by 0.80 V relative to its corrosion potential under simulated solar light illumination which is the record PCP potential among reported works. Based on comprehensive electrochemical and theoretical studies, the origin of the enhanced photo-generated carriers’ separation and depletion to the coupled metals is attributed to a synergic effect between PEF (the spontaneous polarization of BTO) and internal electric field (IEF) resulting from the cascade energy band alignment. Various promising applications can be envisioned from as-proposed multilayered coaxial nanorod array photoelectrodes.