Black Phosphorus Quantum Dot-Sensitized TiO₂ Nanotube Arrays with Enriched Oxygen Vacancies for Efficient Photoelectrochemical\nWater Splitting

Abstract

Photon absorption,\ncharge separation and transportation, and charge-induced\nreactions at the active sites are the main crucial factors involved\nin the photoelectrochemical (PEC) water splitting. Herein, a combination\nof black phosphorus quantum\ndot (BPQD) sensitization and defect engineering strategies is employed\nto optimize the PEC performance of one-dimensional TiO₂ nanotube array (NTA) photoanodes. The as-prepared TiO_2–<i>x</i>/BP electrode exhibits a strong photocurrent density\nunder simulated solar light irradiation, which is almost ∼3\ntimes higher than that of bare TiO₂. Specifically, the\nphotocurrent increment of TiO_2–<i>x</i>/BP is even larger than the sum of TiO_2–<i>x</i> and TiO₂/BP, verifying the synergistic effect of\noxygen vacancies and BPQD sensitization. The maximum photoconversion\nefficiency of TiO_2–<i>x</i>/BP is as high\nas 0.35%, while the value of TiO₂ NTAs is calculated to\nbe 0.13%. The results reveal that oxygen vacancies and BPQDs in the\nTiO_2–<i>x</i>/BP composite not only facilitate\nthe charge separation and transportation but also enhance the activity\nand quantity of reactive sites for water oxidation. The present strategy\nmight open new routes to develop high-performance photoelectrodes\nfor water splitting.