Rich N-Doped Pt–Co Bimetallic Carbon-Nanotube-Based Electrocatalyst for Selective Formaldehyde Sensing

Long-term exposure to formaldehyde (HCHO) in indoor environment poses a serious threat to human health. Despite recent advances, conventional electrochemical HCHO sensors face significant challenges in sensitivity, selectivity, and stability, primarily due to competitive adsorption of interfering species and strong binding of reaction intermediates on the catalyst surface. To address these limitations, we developed an ammonia-assisted bimetallic synergistic templating method to construct a Pt-Co bimetallic and nitrogen-doped carbon nanotube (Pt_2.32Co-N₁₀/CNT) electrocatalyst. Compared to commercial Pt/C, the Pt_2.32Co-N₁₀/CNT exhibits a 2.73-fold higher catalytic activity, a sensitivity of 458.62 μA·mmol/(L·cm²) (4.12 times that of Pt/C), and anti-interference performance. The CNT provides a one-dimensional and high-surface-area structure that accelerates electron transfer and promotes uniform dispersion of active sites, including Pt/Co nanoparticles and Pt/Co single atoms. Importantly, the nitrogen-rich environment forms strong coordinate bonds with Pt and Co, finely-modulating their electronic configurations to suppress methanol interference via selective adsorption. Additionally, nitrogen doping effectively weakens the CO adsorption energy, mitigating the CO-induced catalyst poisoning. With integration with screen-printed electrodes, the portable Pt_2.32Co-N₁₀/CNT sensor achieves a high sensitivity of ca. 2.38 nA/ppb and retains over 96% of its initial response after 7 days, alongside a 10-fold improvement in anti-interference ability in the alcohol-rich environment. This advancement holds transformative potential for next-generation electrochemical sensors with broad applications in environmental health, medical diagnostics, and food safety.