Black phosphorus: A promising nonmetallic doping source for enhancing visible light photoelectrocatalytic water splitting performance of TiO2 nanotube array-based photoanodes

The doping of non-metallic phosphorus into TiO₂-based photoelectrocatalysts is a promising strategy to improve their performance, yet it encounters challenges related to high doping levels, stability, and hydrogen production durability. To address these issues, a novel one-step method was developed to synthesize black phosphorus-doped TiO₂ nanotube arrays (BP-TNTA) under high-pressure and low-temperature conditions within a confined space. The method successfully produced BP-TNTA with tunable phosphorus content and high crystallinity at 600℃. The resulting BP-TNTA exhibited superior photoelectrocatalytic performance, with a 4.4-fold increase in photocurrent density (46.3 μA cm⁻²) under simulated sunlight compared to undoped TNTA (10.5 μA cm⁻²). The enhanced visible light activity is attributed to the introduction of multiple impurity energy levels by BP-doping and Ti³⁺ states, which narrows the band gap and extends the visible light response. Additionally, the Schottky junction between BP-TNTA and the Ti substrate improves the separation and transmission efficiency of photogenerated carriers. This study offers valuable insights for the advancement of robust P-TiO₂-based photoanode materials.