Interface engineering of mesoporous SnO2/TiO2 heterojunction with tailored defects for light-motivated gas sensor

Abstract The convergence of embodied intelligence, neuromorphic computing, and the Internet of Things has propelled intelligent gas sensors to the forefront of artificial olfaction, enabling adaptive, context-aware, and biologically inspired odor perception. Tailoring active sites or defects in sensing materials is an efficient strategy to confer selective gas-surface recognition constitutes for amplifying sensor sensitivity. Herein, a facile ligand-mediated interfacial co-assembly strategy was developed to construct mesoporous crystalline SnO2/TiO2 composites, which enables a composition-dependent structural evolution from Sn-substituted TiO2 solid solutions to well-defined n-n heterojunctions. Density functional theory (DFT) calculations reveal that Sn4+ ions can be substitutionally incorporated into the TiO2 lattice to form charge-balanced Sn-O-Ti bridging units, whereas excessive Sn induces spontaneous phase separation to establish SnO2/TiO2 heterojunctions. The optimized mesoporous hybrids exhibit ∼22-fold higher photocurrent and ∼4-fold stronger light-motivated ethanol sensing response than pristine mesoporous TiO2 under identical conditions. The outstanding performance was attributed to the site-selective doping that effectively tune the local electronic structure and promote the efficient separation and directional transport of photogenerated charges. In-situ doping allows for the tailoring engineering of the pore wall chemical microenvironment, affording an active interface conducive to target gas adsorption and detection reactions. This study establishes a design paradigm for coupling surface reactivity regulation with charge transfer engineering in light-activated gas sensors.