Electrochemical cell for in situ x-ray diffraction under ultrapure conditions

An electrochemical cell has been developed for in situ x-ray diffraction from a working electrode under clean conditions equivalent to ultrahigh vacuum conditions of 5310 mbar. The substrate crystals can be prepared ex situ and transferred into the cell under protection of ultrapure water within a few seconds. The oxygen level in the electrolyte is reduced by continuous N2 flow to less than 0.2% compared to that of a fresh electrolyte. This can be done while rotating the cell by 360° about the surface normal. The electrode potential is accurately measured at the position of the crystal using a Luggin capillary and a standard reference electrode. We demonstrate the performance of our cell by in situ synchrotron x-ray diffraction measurements on ultrathin Co layers electrodeposited on Cu~001! in an aqueous H2SO4 /CoSO4 solution. © 1998 American Institute of Physics. @S0034-6748~98!00204-4#