ABSTRACT The quantum mechanical principles that enhance formaldehyde (CH 2 O) sensing in SnO 2 doped with PdO or ZrO 2 are elucidated using first‐principles density functional theory calculations. The low sensitivity of pristine SnO 2 arises from weak physisorption of CH 2 O, a wide band gap, and electron transfer from CH 2 O to SnO 2 . PdO doping induces strong orbital hybridization between Pd 4d and O 2p orbitals. This reduces the band gap, strengthens chemisorption ( E ads = −0.3214 eV), and enables selective charge transfer differentiation: CH 2 O donates +0.647 e to the surface, while C 2 H 5 OH withdraws 0.360 e. The opposite directions and the fact that the magnitude for CH 2 O (0.647 e) is much larger than that for C 2 H 5 OH (0.36 e) enable genuine intrinsic selectivity against ethanol (S(CH 2 O)/S(C 2 H 5 OH) = 2.14), in contrast to the artifactually high nominal selectivity (10.8) in pristine SnO 2 caused by negligible ethanol response near the detection limit. ZrO 2 doping enhances sensing through a defect‐mediated pathway. It induces lattice distortion and oxygen vacancies, giving the most negative adsorption energy (−0.3812 eV). However, charge transfer magnitudes are comparable for CH 2 O (+0.216 e) and C 2 H 5 OH (−0.38 e), limiting selectivity (intrinsic selectivity of 1.68). Thus, PdO‐SnO 2 is better for fast, stable, and selective detection, whereas ZrO 2 ‐SnO 2 suits trace‐level detection in controlled environments. This work delineates two quantum‐level design paradigms, orbital hybridization and defect engineering, linking atomic modifications to macroscopic sensing performance.
Chen et al. (Wed,) studied this question.