Elucidating the exceptional halide ion etching of bimetallic Ag-Cu oxides for efficient adsorption and porous nanostructure formation

Elucidating the interactions between halide ions and bimetallic oxides can help understand their influences on the physicochemical properties of bimetallic oxides and ultimately lead to better performance, but this has not yet been explored. We report here the first study of the interaction of halide ions with two phase-pure bimetallic Ag-Cu oxides, Ag₂Cu₂O₃ and Ag₂Cu₂O₄, which have different chemical valences of Ag and Cu atoms. We found that halide ions have an aggressive etching effect on both bimetallic oxides, leading to a dramatic evolution of crystal structures and morphology. Halide ions act like “nano-carving knives”, selectively etching out silver atoms to form silver halides and leaving a porous CuO skeleton. We revealed that Ag₂Cu₂O₄ underwent a redox reaction with iodide ions (I⁻) to produce additional I₃⁻ in the solution, which was not observed in Ag₂Cu₂O₃. Interestingly, according to the revealed interactions, both bimetallic oxides are confirmed as superior adsorbents to remove I⁻ from wastewater in terms of a record-high uptake capacity, fast adsorption kinetics, and excellent selectivity for I⁻. Furthermore, such a halide etching can be turned into a powerful synthetic strategy. The out-etched silver halides were dissolved to give robust porous CuO nanostructures, which are proved to be excellent glucose-sensing electrodes with high sensitivity, excellent anti-interference, and stability, showing great application potential. This work contributes to improving the understanding of the mechanisms of halide ion-metal oxide interactions and ultimately to innovative applications.