Oxygen vacancy mediated step-scheme heterojunction of WO2.9/g-C3N4 for efficient electrochemical sensing of 4-nitrophenol

Excitonic effects induced via Coulomb interactions and an appropriate interfacial contact of electrode modified materials play crucial roles in transfer/separation of interfacial charge carriers during the electrochemical sensing process. Herein, an oxygen vacancy (V o ) mediated step-scheme (S-scheme) heterojunction of WO 2.9 /g-C 3 N 4 was fabricated by electrostatic self-assembly of high-purity commercial WO 2.9 nanoparticles and ultrathin g-C 3 N 4 nanosheets, where g-C 3 N 4 nanosheets were prepared via polymerization followed ultrasonic-assisted exfoliation. The fabricated V o -S-scheme WO 2.9 /g-C 3 N 4 heterojunction-based sensor exhibited superior electrochemical performance for detecting environmental hormone 4-nitrophenol (4-NP). Due to the introduction of V o , an increased free-charge-carriers, a built-in electric field and a high adsorption energy are generated at the heterojunction interface, which all can significantly improve the sensitivity of this proposed sensor. It also showed good reproducibility, high accuracy, good recovery, and strong feasibility for 4-NP detection in real samples. This work not only conduces significantly to understanding the defective structures and S-scheme heterojunctions, but also provides new insights into designing and constructing novel efficient electrochemical sensors.