• Yoon, Myung-Han
• Lee, Won-June
• Tricoli, Antonio
• Choi, Jun-Gyu
• Kumar, Priyank
• Yuwono, Jodie
• Abideen, Zain
• Tran-Phu, Thanh
• Nisbet, David

Abstract

The use of heterostructures and surface defect engineering are the two most common techniques for tuning the optoelectronic and photocatalytic properties of metal oxides. Here, we propose a new approach to engineer nano heterojunctions and oxygen vacancies (Vo) at the nanoscale to tune metal oxides' optoelectronic and photocatalytic functions. An ultraporous nano heterostructure composed of NiO-ZnO was synthesized with a porosity of 98% and a grain size of 15 nm, using low-temperature deep UV photoactivation to induce oxygen vacancies. At various etching depths, we observed localized p-n nano heterojunctions and oxygen vacancies originating from both NiO and ZnO. In gas sensing experiments, the nano heterojunctions showed a 30-fold increase in ethanol selectivity and rapid response and recovery to a trace concentration of 20 ppb at room temperature. At an optimal temperature of 150 °C, oxygen vacant nano heterostructures demonstrated a lower limit of detection of 2 ppb, while density functional theory calculations revealed that ethanol adsorption energies on oxygen vacant nano heterostructures increased by 80%, with a 98% increase coming from Vo present at the localized nano heterojunctions. In this work, methods for optimizing metal oxide nanostructures for advanced catalytic applications are presented for designing photocatalytic and optoelectronic properties simultaneously.

Topics

• density
• surface
• grain
• grain size
• theory
• experiment
• Oxygen
• etching
• defect
• density functional theory
• porosity