Electrodeposition of a Mn-Cu-ZnO hybrid material for supercapacitors: a study based on soft X-ray fluorescence and absorption microspectroscopy

Synchrotron-based soft-X-ray imaging and microspectroscopy with sub-micrometer spatial resolution are used to investigate the electrodeposition of Mn-Cu-ZnO, a prospective active material for supercapacitors. This study is focused on the correlation of the local current density and the spatial distribution of the composition and chemical-state in electrodeposits grown potentiostatically at -0.7V (vs a saturated calomel electrode), as well as the optimal potential for the achievement of high specific capacitance and cycling stability. The morphology, elemental distribution, and the local chemical state of both the electrode deposits and the grown dendrite structures are followed by using X-ray imaging, X-ray fluorescence mapping, and X-ray absorption microspectroscopy. For transmission soft-X-ray measurements, a thin-layer Hull-type microcell is developed and fabricated by using electron-beam lithography. The information obtained for the spatial distribution of the deposit is complemented by using electrochemical measurements and numerical simulations.