Oxygen vacancies and N-doped carbon layer synergistically enhance singlet oxygen generation over BiOCl for efficient pollutant degradation

Photocatalytic activation of molecular oxygen (O₂) into reactive oxygen species (ROS) is pivotal for water purification, yet achieving selective ROS generation remains challenging. In this work, we successfully fabricated N-doped carbon-coated BiOCl (BNC) photocatalysts featuring abundant surface oxygen vacancies (OVs), a unique structure that synergistically enhances excitonic effects and promotes singlet oxygen (¹O₂) generation. The N-doped carbon layer synergistically with OVs boosts ¹O₂ generation by facilitating spin–orbit coupling, reducing the singlet–triplet energy gap by 36% to promote intersystem crossing, and enhancing O₂ chemisorption/activation by O–O bond lengthening to 1.52 Å, resulting in a tenfold ¹O₂ yield increase over pristine BiOCl. Optimized BNC10 sample completely degraded ciprofloxacin in 60 min under visible-light irradiation, with 6.9-fold higher rate constant, showed > 87% removal in real waters. Toxicity assessments confirmed the low ecological risk of degradation intermediates, while mineralization experiments demonstrated 80% total organic carbon (TOC) removal. This work provides a novel strategy for excitonic regulation in 2D semiconductors, advancing the design of selective photocatalysts for sustainable environmental remediation.

Graphical Abstract

Boosted energy-transfer-mediated molecular oxygen activation by coating N-doped carbon layer endows BiOCl with high yield of ¹O₂ toward efficient degradation of various pollutants.