Anti-sulfur poisoning electrochemical sensor for sulfur ions based on nitrogen-doped graphene-encapsulated cobalt-nickel nanoparticles

Electrochemical sensor for S^2- based on a novel anti-sulfur poisoning strategy of “chainmail for material” was developed. Nitrogen-doped graphene-encapsulated cobalt-nickel nanoparticles (CoNi@NGs) was synthesized and used as sensing material. The graphene shells can physically isolate the core metal from the external environment to prevent formation of metallic sulfides and corrosion. In addition, CoNi@NGs is sulfurophobe and therefore repels sulfur, resulting in a self-cleaning process. Therefore, the developed sensor exhibited much better anti-sulfur poisoning performance than those reported in the literatures, as the current didn’t decrease after continuous detection of S^2- 80 h with a self-developed on-line flow measurement system. The sensor had a wide S^2- detection range (from 0.5 to 1000 μM) with LOD of 0.47 μM (S/N=3). It was worth mentioning that the sensor showed excellent specificity to S^2- with selectivity of more than 100 to the common interfering substances in water. Finally, the developed sensor was applied to detect S^2- in real water samples including industrial wastewater, pond water and seawater with recoveries of 86.9–118.1 %.