Electrochemical incorporation of hemin in a ZnO–PPy nanocomposite on a Pt electrode as NOx sensor

An electrochemical NOx sensor was fabricated based on the incorporation of hemin on a ZnO–PPy nanocomposite modified Pt electrode. Scanning electron microscopy, energy dispersive X-ray analysis and cyclic voltammetry were used to confirm the successful stepwise assembly procedure for the sensor. The electrocatalytical behavior of the sensor was investigated by cyclic voltammetry. The hemin–ZnO–PPy–Pt electrode exhibited characteristic hemin reversible redox peaks at 0.035 V and −0.11 V vs. Ag/AgCl respectively. The hemin–ZnO–PPy–Pt electrode exhibited 3-fold enhanced electrocatalytic activity towards NOx compared to the hemin–PPy–Pt electrode. The electrocatalytic response of the sensor was proportional to the NOx concentration in the range of 0.8 to 2000 μM (r2 = 0.9974) with a sensitivity of 0.04 μA μM−1 cm−2 and detection limit of 0.8 μM for the hemin–ZnO–PPy–Pt electrode. The low detection limit, wide linear range and enhanced sensitivity of the present sensor make it valuable for potential applications. In addition, this sensor exhibited good reproducibility and stability.