Amorphous a -Cr ₂ O ₃ Nanosheets for NO ₂ and NH ₃ Gas Sensing

High Resolution Image Download MS PowerPoint Slide The design of bidimensional materials with unique catalytic properties has recently focused on the synthesis and applications of layered (2D) amorphous ( a ) metal oxide (2D a -MOx) interfaces. Herein, we report an original strategy for synthesizing bidimensional (2D) amorphous Cr 2 O 3 (2D a- Cr 2 O 3 ) via “low-temperature” annealing of liquid-phase exfoliated anhydrous CrCl 3 transition metal trihalide (TMTH), yielding p- type semiconductor interfaces with excellent NO 2 and NH 3 gas-sensing capabilities. By tuning the annealing time at temperatures below the recrystallization of a -Cr 2 O 3, the removal of chlorine atoms and the complete oxidation/amorphization of CrCl 3 into a -Cr 2 O 3 are achieved. Moreover, the oxidation/amorphization proceeds from the flake’s edge toward the core, following a “Shrinking core” kinetic oxidation model, which preserves the shape of pristine 2D CrCl 3 . Gas-sensing characterization of a- Cr 2 O 3 to NO 2 and NH 3 exhibits enhanced signal gains of 18% (1 ppm of NO 2 ) and 45% (100 ppm of NH 3 ) compared to pristine CrCl 3 . Our research offers valuable insight for extending the “low-temperature” amorphization strategy to the synthesis of 2D amorphous metal oxides ( a- MOx where M = Ni, Co, Fe, Bi, Ti), departing from anhydrous transition metal chlorides, such as NiCl 2, CoCl 2, and oxychlorides, including FeOCl, BiOCl, and TiOCl, broadening the scope and applications of a -MOx interfaces.