A highly sensitive electrochemical sensor for Cd(II) based on protic salt derived nitrogen and sulfur co-doped porous carbon

Lately, an “all-in-one” strategy via direct pyrolysis of protic salt has attracted great attention in the preparation of hetero-doped porous carbons due to its distinctive simplicity. However, protic salt derived carbons usually process large grain sizes thus hamper their applications. Herein, a protic salt derived N, S co-doped porous carbon (N, S-PC) with improved porosity was synthesized by nanocasting and carbonization of protic salt. In the nanocasting silica sphere was used as auxiliary template and an easily obtained protic salt ([pPDA][nHSO₄]) was served as C, N and S sources. The obtained N, S-PC contains rich N, S contents and hierarchical textural porosity, thus favors the electrochemical detection of toxic cadmium ions. The N, S-PC based sensor shows excellent sensitivity and selectivity for Cd(II) versus other metals, with a low detection limit of 0.1 μg L⁻¹ (S/N = 3) over a wide concentration range of 4–80 μg L⁻¹. Applications of the N, S-PC based sensor for Cd(II) assay in tap water samples achieved results with good recoveries, indicating that the N, S-PC based electrode is promising in real sample analysis.