Electrochemical and Photoelectrochemical Bimodal Sensor Based on Copper Modified g‐C₃N₄ for Nitrate Detection

Abstract Nitrates (NO 3 ‐ ) are crucial in agricultural practices and the food industry, but their excessive presence in water can lead to adverse health effects. Their leaching into water sources necessitates regular monitoring. This study introduces a novel bimodal electrochemical (EC)/photoelectrochemical (PEC) sensor, utilizing copper‐modified graphitic carbon nitride (Cu/g‐C 3 N 4 ), designed for precise nitrate determination. The structural morphology and chemical composition of the Cu/g‐C 3 N 4 nanocomposite were meticulously examined using Transmission Electron Microscopy (TEM) and Fourier‐transform infrared spectroscopy (FTIR). The optimization of copper loading in g‐C 3 N 4 was conducted, and the electrochemical behavior and light irradiation interaction of various Cu/g‐C 3 N 4 nanocomposites were systematically studied. The investigation revealed that 20 % Cu/g‐C 3 N 4 represented the optimal doping ratio, establishing the most promising candidate for NO 3 ‐ . Nitrates were consistently measured using both EC and PEC techniques, yielding Limits of Detection (LoD) of 3.75 and 9.60 ppm, respectively. The sensor‘s robust performance was further demonstrated in the presence of possible interferents. The proposed sensors were also successfully used to detect NO 3 ‐ in commercial water. This bimodal sensor presents a promising approach for accurate nitrate determination, attesting to its potential for effective cross‐validation.