Enhancing Amperometric\nOzone Gas Sensing with Room-Temperature\nIonic Liquids and Platinum-Based Electrodes

Ozone (O<sub>3</sub>) poses serious health risks, prompting\nnumerous\ncountries to implement regulations that establish exposure limits\nand emission controls, for example, the air quality index (AQI) for\nO<sub>3</sub> ranging from 50 to 150 parts per billion (ppb), with\nnatural\nlevels at around 30 ppb. Electrochemical sensors are favored for detecting\npollutant gases due to their high sensitivity, low cost, portability,\nenergy efficiency, and capability for selective detection. In this\nstudy, we developed an O<sub>3</sub> sensor employing carbon-supported\nPt-based binary and ternary nanorods\n(NRs) combined with room-temperature ionic liquids (RTILs) as electrolytes,\naiming at highly sensitive and selective detection of O<sub>3</sub> at ppb levels. Initial screening of\nthe O<sub>3</sub> sensing performance across different electrolytes\nidentified H<sub>2</sub>SO<sub>4</sub> and [C<sub>4</sub>mpyrr][NTf<sub>2</sub>] (BMP) as the most sensitive options. BMP outperformed H<sub>2</sub>SO<sub>4</sub> in terms of linearity, selectivity, reproducibility,\nand response/recovery times, despite a relatively lower sensitivity.\nElectrochemical testing of Pt, PtAu, PtAg, and PtAuAg NR electrodes\nin BMP revealed that the addition of Au enhanced the linear response,\nwhile Ag improved sensitivity. Consequently, the ternary PtAuAg NR\nelectrode exhibited the highest sensitivity (10.5 nA/ppm (parts per\nmillion)) and a broad detection range, fulfilling the AQI requirements\nfor O<sub>3</sub>. The current response from the PtAuAg NR electrode\nclosely aligned with results from an ultraviolet (UV) photometric\nanalyzer, confirming its accuracy. Notably, this electrode contains\nonly 20 wt % noble metals, which reduces the overall cost to just\n11% of that of a traditional pure Au electrode.