Enhanced electrocatalytic activity in MOFs-derived 3D hollow NiCo-LDH nanocages decorated porous biochar for simultaneously ultra-sensitive electrochemical sensing of Cu and Hg.

Layered double hydroxides (LDHs) have attracted significant attention due to their compositional and structural flexibility. However, it is challenging but meaningful to design and fabricate hierarchical mixed-dimensional LDHs with synergistic effects to increase the electrical conductivity of LDHs and promote the intrinsic activity. Herein, 3D hollow NiCo-LDH nanocages decorated porous biochar (3D NiCo-LDH/PBC) has been synthesized by using ZIF-67 as precursor, which was utilized for constructing electrochemical sensing platform to realize simultaneous determination of Cu and Hg. The 3D NiCo-LDH/PBC possessed the characteristics of hollow material and three-dimensional porous material, revealing a larger surface area, more exposed active sites, and faster electron transfer, which is beneficial to enhancing its electrochemical performance. Consequently, the developed sensor displayed good performance for simultaneously detecting Cu and Hg with ultra-low limit of detection (LOD) of 0.03 μg L and 0.03 μg L, respectively. The proposed sensor also demonstrated excellent stability, repeatability and reproducibility. Furthermore, the sensor can be successfully used for the electrochemical analysis of Cu and Hg in lake water sample with satisfactory recovery, which is of great feasibility for practical application.