Tailored Nitrogen Sites on Activated Carbon for Enhanced Formaldehyde Detection at Room Temperature

Abstract

This research introduces nitrogen atom into activated (AC) to enhance their sensitivity to formaldehyde vapor. Nitrogen-doped activated carbon (N-AC) was successfully prepared by heat treatment with ammonia (NH₃) at 800°C. The atomic ratio of nitrogen to carbon in N-AC is approximately 4.1 at%. AC and N-AC were separately mixed with ethanol and then dropped onto printed circuit board with Au/Cu electrodes, serving as the sensor substrate. As-fabricated AC and N-AC sensors were exposed to formaldehyde concentrations ranging from 1 to 100 parts per million (ppm) at room temperature. As-fabricated N-AC sensor demonstrated a sensor response approximately 5- to 6-fold higher than that of the AC sensor. The enhancement of formaldehyde sensitivity is attributed to the increased surface area, porosity and nitrogen doping into AC. The sensing mechanism can be explained by charge transfer from formaldehyde molecules to sensing materials. Nitrogen-doped sites play a crucial role in improving formaldehyde adsorption due to their high binding energy and significant charge transfer, resulting in an enhanced sensor response. This work proposes an effective method involving NH₃ heat treatment for biomass-derived AC to improve surface area, porosity, and nitrogen doping of AC to enhance the sensitivity of formaldehyde detection at room temperature.