Sensitive detection of Hg(II) on MoS/NiS based on interfacial engineering to accelerate the Ni/Ni cycle: Identification the role of atomic-level heterojunction-induced electron transfer in electroanalysis.

The valence change of transition metal ions in nanomaterials can highly enhance the electrochemical detection performance toward heavy metal ions (HMIs), and how to further promote the valence change calls enormous concerns in electroanalysis. In this work, an interfacial engineering that combing the MoS and NiS together to form the MoS/NiS complex is proposed. The density functional theory (DFT) results reveals that the novel atomic-level heterojunction between MoS and NiS will build an internal electric field (IEF), which leads to an enhanced conductivity and valence change behavior of Ni atoms in MoS/NiS complex, resulting in a superior detection performance. In detail, the formation of atomic-level heterojunctions in the MoS/NiS complex accelerates electron transfer due to the valence changes associated with Ni/Ni cycling. The active Mo species on MoS act as electron donors, facilitating the reduction of Ni to Ni on NiS, thereby promoting Ni/Ni cycling. As anticipated, the MoS/NiS complex exhibits exceptional detection performance for Hg(II), with a sensitivity of 459.13 μA μM cm, surpassing even that of other composite materials. In general, these findings are expected to significantly advance the application of electron transfer acceleration in electroanalysis based on the construction of heterojunction.