Side-Adsorption Catalysis at Fe-N ₄ Diatomic Sites Enables Ultrasensitive Electrochemical Detection of Chlorogenic Acid

Chlorogenic acid (CGA) has antibacterial, antiviral, and antioxidant properties, making its detection essential in food science, pharma, and environmental monitoring. Nevertheless, the mechanistic understanding of CGA recognition and redox behavior at electrochemical sensor interfaces remains limited, posing a key scientific challenge. Herein, a novel Fe-N4 diatomic-site carbon nanomaterial is prepared via in situ pyrolysis of coffee grounds, which served as a simultaneous precursor for carbon, iron, and nitrogen. Aberration-corrected scanning transmission electron microscopy confirms single-atom dispersed iron with diatomic active sites. At the same time, X-ray absorption near-edge structure and extended X-ray absorption fine structure analyses reveal a Fe–N4 coordination. Density functional theory calculations indicate that during CGA oxidation, hydroxyl oxygen atoms preferentially adopt a side-adsorption configuration at dual active sites, thereby enhancing interfacial electron transfer and catalytic selectivity. The constructed electrochemical sensor exhibits two linear response ranges, 0.2−0.8 and 0.8−500.0 μmol/L, with a detection limit of 0.067 μmol/L (LOD = 3 s/m). Overall, this study presents a sensitive, cost-effective electrochemical sensor for CGA detection and highlights the critical role of adsorption configuration in determining the performance of single-atom catalysts.