Ultrafast Joule heating synthesizing (Co, Ni, Zn)Cr2O4 nanomaterials for high xylene gas sensing properties

The valence electron configuration largely determines the performance of functional materials, in which different electron spin and orbital occupancy would induce diverse phenomena. Herein, the study of 3d electronic configuration dominant gas sensing selectivity is presented. Utilizing ultrafast Joule heating, transition metal spinels XCr 2 O 4 (X = Co, Ni, Zn) have been synthesized and consistently exhibit sensing selectivity toward xylene gas. The e g empty orbitals of Cr 3+ 3 d 3 (t 2g 3 e g 0 ) tend to overlap with the π orbitals of xylene molecules, achieving stable xylene adsorption and electron transfer and thus presenting remarkable xylene gas sensing selectivity. The valence electron configurations of 3 d 7 , 3 d 8 and 3 d 10 for Co 2+ , Ni 2+ and Zn 2+ result in a progressively lower response to xylene gas. This valence electron configuration perspective is experimentally supported by gas sensing selectivity of XFe 2 O 4 (X = Co, Ni, Zn) toward acetone molecules, in which the electronic orbital configuration of Cr 3+ 3 d 3 of B sites is replaced by Fe 3+ 3 d 5 . Theoretically, density functional theory (DFT) calculations based on adsorption energy and charge density difference confirm the strong adsorption of xylene at Cr 3+ sites and efficient electron transfer from xylene to Cr sites. Download: Download high-res image (422KB) Download: Download full-size image