Enhancing Amperometric Ozone Gas Sensing with Room-Temperature Ionic Liquids and Platinum-Based Electrodes

Abstract

Ozone (O₃) poses serious health risks, prompting numerous countries to implement regulations that establish exposure limits and emission controls, for example, the air quality index (AQI) for O₃ ranging from 50 to 150 parts per billion (ppb), with natural levels at around 30 ppb. Electrochemical sensors are favored for detecting pollutant gases due to their high sensitivity, low cost, portability, energy efficiency, and capability for selective detection. In this study, we developed an O₃ sensor employing carbon-supported Pt-based binary and ternary nanorods (NRs) combined with room-temperature ionic liquids (RTILs) as electrolytes, aiming at highly sensitive and selective detection of O₃ at ppb levels. Initial screening of the O₃ sensing performance across different electrolytes identified H₂SO₄ and [C₄mpyrr][NTf₂] (BMP) as the most sensitive options. BMP outperformed H₂SO₄ in terms of linearity, selectivity, reproducibility, and response/recovery times, despite a relatively lower sensitivity. Electrochemical testing of Pt, PtAu, PtAg, and PtAuAg NR electrodes in BMP revealed that the addition of Au enhanced the linear response, while Ag improved sensitivity. Consequently, the ternary PtAuAg NR electrode exhibited the highest sensitivity (10.5 nA/ppm (parts per million)) and a broad detection range, fulfilling the AQI requirements for O₃. The current response from the PtAuAg NR electrode closely aligned with results from an ultraviolet (UV) photometric analyzer, confirming its accuracy. Notably, this electrode contains only 20 wt % noble metals, which reduces the overall cost to just 11% of that of a traditional pure Au electrode.