Manipulating interface built-in electric fields for efficient spatial charge separation in hematite-based photoanodes

Herein, a novel strategy of interface charge modulation for manipulating interface built-in electric fields (IEFs) and boosting spatial charge separation is introduced to alleviate charge recombination in the bulk and at the surface of hematite photoanodes. Hydrothermally grown Ti-doped hematite (Hem) nanorods are decorated with graphitic carbon nitride (g-C₃N₄) species and small molybdenum oxide (MoO₃) clusters using a facile two-step dip-coating process. Compared with the pristine Hem, the obtained Hem/C₃N₄/MoO₃ exhibits increased photoelectrochemical water splitting performance with its photoanodic current density remarkably increased from 0.3 to 1.6 mA cm⁻² at 1.23 V versus reversible hydrogen electrode (RHE) and incident photon-to-current conversion efficiency reaching 18.4% at 1.23 V versus RHE at 300 nm. The IEFs are introduced in the Hem/C₃N₄/MoO₃ heterojunction by modulating the interfacial charge property via a type II band alignment at the Hem/C₃N₄ interface and an enhanced band bending at the surface of the photoanode, which substantially promote the spatial charge separation. By relieving the bottleneck of charge carrier transfer dynamics, this work in interfacial charge modulation provides a facile and effective strategy to boost the spatial charge separation in Hem-based photoanodes and other semiconducting devices for efficient solar energy conversion. [Figure not available: see fulltext.].