Mechanistic Insights into Heterogeneous Electron Transfer Kinetics of TiCT and VCT MXene-Based Nanoelectrodes: An Electrochemical and DFT Correlation.

MXene (transition metal carbides/nitrides) exhibits promising physical and chemical properties due to its layered nanosheet-like morphology and high surface area and the presence of surface functional groups that are essential for developing efficient electrochemical sensing devices that can function reliably in on-field or real-time conditions. However, the understanding of the heterogeneous electron transfer (HET) mechanism in MXene, particularly the electrode-electrolyte interface, remains limited within the scientific community. In this study, we conduct an in-depth investigation of the basic chemistry behind the electron transfer kinetics of TiCT and VCT MXene, respectively, on carbon screen-printed electrodes (CSPE). The HET kinetics was thoroughly studied by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which was correlated with the electronic density of states (eDOS) of the two MXenes via density functional theory (DFT). It was observed that TiCT-modified nanoelectrodes exhibit an enhanced electron transfer rate ( ∼0.03 cm/s) as compared to VCT nanoelectrodes ( ∼0.0064 cm/s). This is primarily attributed to higher quantum capacitance ∼ 356 nF in the former due to increased eDOS, as evidenced by DFT simulations. The current study suggests that TiCT MXene exhibits superior HET kinetics compared to VCT MXene. Hence, the TiCT MXene can be efficiently utilized in development of electrochemical sensors.