Performances of Nano-Structured Cu2O Thin Films Electrochemically Deposited on ITO Substrates in Lactate Bath as Liquid Petroleum Gas Sensors

Abstract

The investigations are focused on structural and surface morphological features and their influence on electrical and wetting characteristics against liquid petroleum gas (LPG) sensing of synthesized nanostructured cuprous oxide (Cu2O) thin films grown by electrochemical deposition (ECD) on indium tin oxide (ITO) glass substrates in lactate bath (pH 10). p-Cu2O films revealed a cubical-tetrahedron nano-scale polycrystalline grain distribution (average grain size: 64.2 nm, inter planer spacing: 0.24 nm) that exhibited dominance in the crystallographic plane (111). LPG sensing evaluations of p-Cu2O/ITO done at 70 °C constant temperature with 100% LPG at 5 cc min−1 flow rate, showed excellent gas sensor response, recovery, and stability over time due to its moderate wetting behavior (average contact angle: ∼86°). AC impedance measurements carried out at room temperature demonstrated an ionic to electronic conduction variation from 100 Hz to 1 MHz, due to adsorption/desorption of LPG molecules (CnH2n+2) and oxygen species on the nano-particles surface. Cu2O/ITO flat band potential was found to be higher than its’ ambient state after exposure to LPG with an increment in acceptor density. Overall, this efficient LPG sensing could be attributed to the interfacial properties of Cu2O thin films and ITO substrates, that provide an optimized fabrication process of nano-structured Cu2O thin films.