Switching N2O Adsorption Geometry from the O-End to the N-End on Au Nanoparticle-Decorated ZnO Enables Enhanced Sensing Performance

Abstract

Nitrous oxide (N2O) is a potent greenhouse gas, but its chemical inertness hinders sensitive chemiresistive sensing. We demonstrate here that Au-decorated ZnO (Au-ZnO) dramatically enhances N2O detection. At an operating temperature of 260 °C, the Au-ZnO sensor responds to 25 ppm N2O with a value of 7.6, which is a 3.8-fold enhancement over the ZnO sensor. It also exhibits high selectivity against common greenhouse gases, a lower theoretical limit of detection (0.24 ppm), a fast response time (10 s), and reliable stability. The previously elusive mechanism has been uncovered by integrating experimental characterizations and density functional theory calculations. A strong metal–support interaction, abundant oxygen vacancies at the Au-ZnO interface, and an electron-rich surface collectively switch N2O adsorption geometry from the O-end (physisorption on ZnO) to the N-end (weak chemisorption on Au-ZnO). This switch induces significant intramolecular charge rearrangement of N2O, which is crucial for enhancing the selective N2O sensing reaction. The abundance of reactive sites, the spillover effect, and the catalytic action of Au nanoparticles, as well as the narrowed band gap, promote N2O adsorption, surface reactions, and rapid charge transfer collectively. This work goes beyond the traditional oxygen-ionosorption model by showing that switching adsorption geometry and intramolecular polarization are crucial for activating inert molecules. This provides a detailed explanation of how to create high-performance N2O sensors.