Ultra-sensitive electroanalysis of toxic 2,4-DNT on o-Co_xFe_1-xSe₂ solid solution: Fe-doping-induced c-CoSe₂ phase...

How to achieve the sensitive electroanalysis of organics pollution in water environment is vital significance, but it is limited by their redox inert and the ambiguous detection mechanism. Herein, Fe-doping-induced structural phase transition engineering is designed to make the cubic (c-) CoSe₂ to orthorhombic (o-) CoSe₂, accompanying with the formation of o-Co_xFe_1-xSe₂ solid solution. By controlling the Fe doping amount, the fully orthogonalized C1F1 (the mole ratio of Co/Fe is 1:1) electrode acquires a high sensitivity of 0.293 μA μM^-1 toward 2,4-Dinitrotoluene (2,4-DNT) detection. Besides, C1F1 exhibits excellent stability, reproducibility and practicality for 2,4-DNT detection. Combined with experimental studies and theoretical calculations, it is shown that during the phase transition, electrons are transferred from Co to Fe, forming electron-rich Fe active sites. The Fe sites can match well with free 2,4-DNT molecules and then accelerate the reduction process of 2,4-DNT. A series of experiments including DFT and electrochemistry demonstrate that the doping-induced structural phase transition strategy can improve the adsorption performance of the material and also enhance the catalytic ability, thereby enhancing the electrochemical sensitivity. The co-engineering of morphology and phase transition of metal selenides by doping will provide inspiration for the design of sensitive sensing interfaces for organic pollutants.