Doping assisted interfacial engineering improves the photoelectrochemical performance of titanium dioxide photoanodes

Titanium dioxide (TiO₂) is a widely studied photoanode material for photoelectrochemical (PEC) water splitting, however, its performance is often hindered by severe charge carrier recombination. To address this limitation, a novel composite photoanode comprising indium-doped TiO₂ (In-TiO₂), polyaniline (PANI), and cobalt phosphate (CoPi) was developed. In this material system, In³⁺ doping effectively modulates the electronic structure of TiO₂, elevating its work function and facilitating bulk charge separation while mitigating Fermi level pinning. The PANI interlayer functions as an efficient hole transport medium, and CoPi acts as an oxygen evolution reaction (OER) co-catalyst, providing abundant active sites and accelerating surface reaction kinetics. Moreover, the formation of strong Co-N interactions between PANI and CoPi enhances interfacial charge transfer, further boosting PEC activity. As a result, the optimized In-TiO₂/PANI/CoPi photoanode delivers a photocurrent density of 4.0 mA·cm^-2 at 1.23 V vs. RHE and achieves a solar-to-hydrogen (STH) efficiency of 1.72 %. This synergistic design strategy offers a promising pathway for the development of efficient and stable photoanodes for solar-driven water splitting.