The real time electrodeposition of potassium has been monitored for the first time in an ionic liquid using in situ electrodeposition-X-ray photoelectron spectroscopy (XPS). The ionic liquid used was N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C(4)mpyrr][NTf2]), and electrodeposition occurred at a nickel mesh electrode. Potassium electrochemistry was monitored at the ionic liquid-vacuum-electrode interface using a novel cell design. (C) 2011 Elsevier B.V. All rights reserved.