Mg deposition observed by in situ electrochemical Mg K-edge X-ray absorption spectroscopy

► An in situ electrochemical X-ray absorption cell has been developed. ► Magnesium deposition was confirmed by Mg K-edge absorption spectroscopy and X-ray diffraction. ► Potentiostatic in situ experiments revealed the presence of an intermediate at the interface of the working electrode. ► Mg-dimer electrolyte is not the active species at the interface of Mg deposition.