In situ infrared subtractive normalized Fourier transform infrared spectroscopy (SNIFTIRS) experiments were performed simultaneously with the electrochemical experiments relevant to Li-air battery operation on gold cathodes in ionic liquid PYR14TFSI based electrolyte. Ionic liquid anion was found to be stable, while the cation PYR14+ was found to decompose in studied conditions. In oxygen saturated LiTFSI containing PYR14TFSI electrolyte carbon dioxide and water were formed at potential 4.3 V either with or without previous oxygen electro-reduction reaction. However in deoxygenated LiTFSI contacting ionic liquid no formation of CO2 or water was observed, suggesting oxygen presence to be crucial in carbon dioxide production. (C) 2017 The Electrochemical Society. All rights reserved.