Flower-like g-C3N4/TiO2 array sensor integrated with a flow injection thin-layer cell for continuous and sensitive photoelectrochemical detection of copper ions

A flow injection photoelectrochemical (FI-PEC) system for the rapid, sensitive, and continuous detection of copper ions (Cu 2 + ) in aqueous solutions was developed. The PEC system integrates a custom-designed 3D-printed thin-layer flow cell (volume of 390 µL), enabling efficient mass transfer. The PEC sensor is based on a g-C 3 N 4 /TiO 2 heterojunction photoanode, which was synthesized in situ on a fluorine-doped tin oxide (FTO) substrate via hydrothermal and calcination processes. The obtained g-C 3 N 4 /TiO 2 composite has a flower-like array structure and exhibits enhanced photo response under illumination, with a photocurrent density of 0.34 mA/cm 2 . The g-C 3 N 4 /TiO 2 PEC sensor can be efficiently regenerated using EDTA, allowing for multiple detection cycles without significant performance degradation. The system demonstrates a wide linear detection range of 0.1–150 µM, a low detection limit of 0.043 µM, excellent selectivity against common interfering ions, and maintains good stability after 10 h of continuous operation. These results indicate that the FI-PEC system based on the g-C 3 N 4 /TiO 2 heterojunction photoanode has practical application prospects in monitoring copper pollution in natural environments.