Modulating the Electron Temperature of Spark Discharge for Highly Efficient Production of HNO<sub>3</sub>.

Song, Zhimin; Qiu, Yifan; Liu, Jiuyi; Kong, Xiangdong; Zhu, Mingyi; Zhu, Xia; Shi, Zhihua; Wang, Cheng et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Low-temperature plasma offers a promising pathway for sustainable production of HNO<sub>3</sub> directly from air and H<sub>2</sub>O under ambient conditions. However, most plasma electrodes suffer from a low yield rate and selectivity of NO<sub>2</sub>, which limits the efficiency of HNO<sub>3</sub> production. In this study, we propose a strategy to improve the NO<sub>2</sub> yield by regulating the electron temperature (<i>T</i><sub>e</sub>) in spark discharge. An array electrode with multiple vertically oriented hollow Cu rods is designed to reduce localized energy deposition and optimize <i>T</i><sub>e</sub>. At an airflow rate of 300 SCCM, the array electrode achieves a yield rate for NO<sub>2</sub> of 17.85 mmol h<sup>-1</sup>, which is 10.8 times higher than that (1.65 mmol h<sup>-1</sup>) of the conventional single electrode. Notably, after absorption in 300 mL of H<sub>2</sub>O, the array electrode produces a pure HNO<sub>3</sub> solution with a concentration as high as 680.5 mM within a 12 h discharge time.