Self-powered sensor based on a TiO2 NTAs/FeN5 SACs photocatalytic fuel cell for sensing chemical oxygen demand

Chemical oxygen demand (COD) is a crucial parameter in assessing water quality. Due to the improved public awareness of environmental protection, the rapid, eco-friendly, and cost-effective methods for COD measurement are highly desired. This work proposes a new self-powered COD sensor (SPCS), based on a photocatalytic fuel cell composed of a FeN 5 single-atom nanozymes (FeN 5 SACs)/ITO cathode and a TiO 2 nanotube arrays (TiO 2 NTAs)/Ti photoanode. Because organic compounds are able to be involved as anodic fuels, the detection of COD with the SPCS could be achieved by simply measuring the deviation in short circuit current. The COD detection range is determined to be from 0.5 to 49.4 mg/L, with the limit of detection of 1.38 mg/L. The SPCS possesses satisfactory anti-interference ability against anions including Cl - and SO 4 2- , and high stability even after 60-day storage. For real sample analysis, satisfactory reproducibility (RSD < 6 %), and low relative error (2.48–6.52 %) have been obtained. Besides, the sensor offers the advantages of cost-effectiveness, environmental friendliness, and fast response (< 1 min). Consequently, the SPCS could be regarded as a promising candidate for the sensing of COD.