Synthesis of Bimetallic (iron–cobalt) Single Atom Catalysts for Electrochemical Detection of Nitrites

Nitrite (NO2-) is responsible for several physiological processes but can be harmful in excess. With rising exposure from food preservatives, fertilizers, and pollutants, accurate nitrite assessment is crucial for health and environmental safety. Different methods have been employed for its determination, with electrochemical sensors showcasing great promise. Single atom catalysts (SACs) are a class of nanomaterials that consists of isolated catalytic metal atoms anchored on conductive supports, which exhibit unique electronic properties with great promise for this application. The performance of these materials can be enhanced even more by incorporating a secondary metal in the catalyst structure. This leads to the creation of more surface-active sites and enables the facilitation of multi-step reactions. Herein, a bimetallic single atom catalyst (FeCoSAN) is synthesized through a single step laser assisted solid-process by anchoring iron and cobalt atoms while simultaneously creating a laser-scribed graphene (LSG) support. The presence of Fe and Co atoms is verified by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption spectroscopy (XANES and EXAFS). Through electrochemical testing, the bimetallic system demonstrated excellent capabilities for determination of NO2, achieving up to 100% more efficiency, in comparison with bare LSG, with a detection limit of 2.42 mu m and a sensitivity value of 515.07 mu A mm-1 cm-2 over a linear range from 5.0 to 1666 mu m. This highlights their potential for in vivo and point-of-care sensing applications.