Acicular Nickel on Carbon Nanofiber as Electrochemical Sensor Electrode for the Rapid Detection of Aqueous and Gaseous Formaldehyde at Room Temperature

The rapid and straightforward detection of formaldehyde (FA) in the environment is crucial for preventing the accidental inhalation of FA and limiting skin exposure to FA. In this study, we developed a simple nickel-based electrocatalytic electrode on carbon nanofibers (CNFs−Ni), which is suitable for rapidly detecting FA at room temperature. Centrifugal electrospinning was used to obtain polyacrylonitrile (PAN) nanofibers, which was subsequently stabilized and carbonized to fabricate the CNFs. Carbonization of the CNFs occurred at various temperatures (T_c=1200, 1300, 1400, and 1500 °C). PAN CNFs served as a highly conductive template for electroless plating under a magnetic field of 500 G to grow acicular nickel. The amperometric responses of the CNFs−Ni to aqueous FA were then measured. A lab-built amperometric gas sensor (CNFs−Ni 1–8), which comprised CNFs with a reduced Ni loading, was used as the electrode for detecting gaseous FA. Scanning electron microscopy (SEM), linear sweep voltammetry (LSV), cyclic voltammetry (CV), and chronoamperometry were used to evaluate the sensitivities of the electrodes. Within the linear range of 0.05–91.5 mM, the CNFs1400-Ni electrode was highly sensitive for detecting aqueous FA (2592 μA mM⁻¹ cm⁻²), as evidenced by the fast response time (6 s). At a low concentration of gaseous FA (0.5 ppm), the laboratory-built FA gas sensor was stable (98.3 %) and had a fast response time (5 s) after 9 h of continuous operation.