Constructing BiOI@Nv/g-C3N4 with S-scheme heterojunction for enhanced photoelectrochemical performances towards highly sensitive and selective detection of trace chlorpyrifos

Chlorpyrifos, one of the organophosphorus pesticide commonly used in the environment, may bring about an irreversible harm such as lung cancer to human body. Photoelectrochemical (PEC) detection techniques based on g-C₃N₄ for sensing chlorpyrifos have attracted increasing attentions, but impeded by several inherent constraints such as a limit of active sites and carriers transfer. To conquer these challenges, a photoelectrochemical sensor of BiOI@N_v/g-C₃N₄ with a step scheme heterojunction was thereby proposed for the sensitive and selective detection of trace chlorpyrifos. Herein, the created N vacancies facilitated the migration of photo-electrons from BiOI to recombine with the holes of N_v/g-C₃N₄ under light irradiation. A powerful oriented built-in electric field was established directing from N_v/g-C₃N₄ to BiOI. The photocurrent intensity of the as-prepared sensor exhibited over 7.6 times higher than that of pure g-C₃N₄, showing a well PEC performance. High selectivity of the developed sensor was attributed to the specific interaction between Bi sites of the developed composites and the S, N atoms in chlorpyrifos. Such sensitive and steady PEC sensor exhibited a linear detection range from 0.01 to 20 ppb with a detection limit of 0.004 ppb. Further, the sensor displayed reliable performance when applied to real river water and soil samples, achieving nice recovery rates. Unlike traditional PEC sensor, this one was prepared into S-scheme heterojunction by creating a N defect-induced driving force based on the altered built-in electric field. The work not only provides experimental evidences but also advances the fundamental theories so as to offer a robust g-C₃N₄-based PEC platform for environmental analysis.