Confined self-assembly of S, O co-doped GCN short nanotubes/EG composite towards HMIs electrochemical detection and removal.

In this paper, we prepared composites by confining S, O co-doped C3N4 short nanotubes (SOT) into the slit holes of expanded graphite (EG). The prepared SOT/EG composites had hierarchical pores. Macroporous and mesoporous were conducive to the permeation of heavy metal ions (HMIs) solution, while microporous were favorable for HMIs capture. In addition, EG had excellent adsorption and conductive properties. By leveraging their synergistic effect, SOT/EG composites could be used for electrochemical detection and removal of HMIs simultaneously. The excellent HMIs electrochemical detection and removal performances were due to the unique 3D microstructure and the increase of active sites such as S and O. When SOT/EG composites were prepared into modified electrodes, the limit of detections (LODs) of Pb2+ and Hg2+ were 0.038 and 0.051 μg L-1 for simultaneous detection and 0.045 and 0.057 μg L-1 for individual detection. When SOT/EG composites were used as adsorbents, the equilibrium adsorption capacity of Pb2+ and Hg2+ solution of 10 mg L-1 could reach 228.0 and 313.1 mg g-1, and the adsorption efficiency was above 90%. Due to the low raw materials cost and simple preparation method, SOT/EG composite is a very promising bifunctional material for HMIs electrochemical detection and removal.