Ultrasensitive, Sustainable, and Selective Electrochemical Hydrazine Detection by ALD‐Developed Two‐Dimensional WO3

Abstract Wafer‐scale two‐dimensional (2D) WO 3 films with different thicknesses of 0.78, 1.4, 3.6, and 6.5 nm were fabricated on Au‐SiO 2 /Si substrates using an atomic layer deposition technique. Their surface morphologies and chemical components were examined by field‐emission scanning electron microscopy, atomic force microscopy and X‐ray photoelectron spectroscopy. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were utilized for the analysis of the electrochemical behavior of 2D WO 3 films towards hydrazine detection under various conditions. The effect of the thickness of 2D WO 3 on the electrochemical performance was also analyzed. Significant improvement in hydrazine sensing capabilities was obtained for monolayer 2D WO 3 (0.78 nm), demonstrating a high sensitivity of 1.24 μA μM −1 cm −2 , a linear hydrazine concentration detection ranging from 0.2 to 2100 μM, great long‐term stability, excellent selectivity and the lowest limit of detection of 0.015 μM reported to date, which provide a great potential method for materials fabrication in the development of high‐performance hydrazine detection.