Sensitive detection of Hg(II) on MoS2/NiS2 based on interfacial engineering to accelerate the Ni2+/Ni3+ 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 MoS2 and NiS2 together to form the MoS2/NiS2 complex is proposed. The density functional theory (DFT) results reveals that the novel atomic-level heterojunction between MoS2 and NiS2 will build an internal electric field (IEF), which leads to an enhanced conductivity and valence change behavior of Ni atoms in MoS2/NiS2 complex, resulting in a superior detection performance. In detail, the formation of atomic-level heterojunctions in the MoS2/NiS2 complex accelerates electron transfer due to the valence changes associated with Ni2+/Ni3+ cycling. The active Mo4+ species on MoS2 act as electron donors, facilitating the reduction of Ni3+ to Ni2+ on NiS2, thereby promoting Ni2+/Ni3+ cycling. As anticipated, the MoS2/NiS2 complex exhibits exceptional detection performance for Hg(II), with a sensitivity of 459.13 μA μM−1 cm−2, 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. [Display omitted] •The MoS2 and NiS2 interfacial engineering effectively improved the electrochemical detection of Hg(II).•The effects of atomic-level heterojunctions generating built-in electric fields are described.•The IEF can enhance the conductivity and valence change behavior of Ni atoms in MoS2/NiS2 complex.•The valence change of MoS2 increases the proportion of Ni2+ with high catalytic activity.•MoS2/NiS2 complex realizes a high sensitivity (459.13 μA μM−1 cm−2) for Hg(II) detection.