Hypersensitized electrochemical detection of Hg(II) based on tunable sulfur-doped porous Co3O4 nanosheets: Promotion Co2+/Co3+ valence change cycle and adsorption via introducing S

Doping can effectively improve the performance of materials used for electrochemical detection, but non-metallic doping is rarely used in this regard, and the related electroanalytical mechanism is still not clear. Herein, a sulfur-doped porous Co3O4 nanosheets is prepared by hydrothermal synthesis. By controlling the amount of doped S, the Co3O4 with 10 mg S-doping (named as SC10) shows rich surface defects and high ratio of Co2+/Co3+, and demonstrates an excellent detection performance toward mercury ion (Hg(II)). Decent structural features of abundant surface defects and porous sheet structure provide more active sites and help the adsorption of Hg(II). Moreover, strong interaction of S and Hg improves the combining of SC10 and Hg(II) to obtain more Hg(II) on the electrode surface additionally. Meanwhile, the facilitated Co2+/Co3+ valence change cycle could also enhance the redox of Hg(II) to Hg(0) in the square wave anodic stripping voltammetry (SWASV) process. Consequently, the as-prepared SC10 modified electrode has an excellent sensitivity of 1027.46 μA μM−1 cm−2 and low LOD of 0.016 μM towards Hg(II). The SC10 shows excellent anti-interference and stability, as well as a satisfactory current response for actual water. This non-metal doped metal oxide is expected to become a promising electrode modification material.