PdCo composite nanoparticle-embedded N-doped carbon nanofibers for electrochemical carbon monoxide detection in physiological media

Precise and selective detection of carbon monoxide (CO) under physiologically relevant conditions is important due to CO's dual role as both a toxic gas and an endogenous gasotransmitter. In this study, PdCo-incorporated nitrogen-doped carbon nanofibers (PdCo/N-CNF_x, where x = 700, 750, 775, and 800 indicates the carbonization temperature in °C) were synthesized via electrospinning and controlled thermal carbonization, using melamine as the nitrogen source. Physical characterizations (SEM, TEM, XRD, XPS) confirmed the well-defined fibrous morphology and uniform metal distribution of the synthesized materials. Among them, PdCo/N-CNF_775 had the highest proportion of quaternary nitrogen species. Notably, PdCo/N-CNF_775 exhibited the highest electrocatalytic activity for CO oxidation under neutral pH and room temperature, achieving a high sensitivity of 0.1432 μA μM⁻¹ and a low detection limit of 0.228 μM, significantly improved compared to the control sample prepared without nitrogen doping. PdCo/N-CNF_775 also exhibited excellent selectivity over other similar gasotransmitters, such as nitric oxide (NO) and hydrogen sulfide (H₂ S), with amperometric selectivity coefficients of −2.8 and − 1.7, respectively. Compared to previously reported CO electrocatalysts, PdCo/N-CNF_775 outperformed in both sensitivity and detection limit under biologically relevant conditions, underscoring its promise for high-performance electrochemical CO sensing in complex physiological environments where CO concentrations are typically very low.