Phosphorus Cation Doping: A New Strategy for Boosting Photoelectrochemical Performance on TiO₂ Nanotube Photonic Crystals

Photoelectrochemical (PEC) water splitting is a promising technique for sustainable hydrogen generation. However, PEC performance on current semiconductors needs further improvement. Herein, a phosphorus cation doping strategy is proposed to fundamentally boost PEC performance on TiO₂ nanotube photonic crystal (TiO₂ NTPC) photoelectrodes in both the visible-light region and full solar-light illumination. The self-supported P-TiO₂ NTPC photoelectrodes are fabricated by a facile two-step electrochemical anodization method and subsequent phosphidation treatment. The Ti⁴⁺ is partially replaced by P cations (P⁵⁺) from the crystal lattice, which narrows the band gap of TiO₂ and induces charge imbalance by the formation of Ti-O-P bonds. We believe the combination of unique photonic nanostructures of TiO₂ NTPCs and P cation doping strategy will open up a new opportunity for enhancing PEC performance of TiO₂-based photoelectrodes.