Pulse-plating of Mn-Cu-ZnO for supercapacitors: a study based on soft X-ray fluorescence and absorption microspectroscopy

This paper reports on the electrodeposition of Mn-Cu-ZnO for hybrid supercapacitors. This material exhibits a dual structure consisting of Mn-rich highly active, but poorly electronically conducting, grains, which are locked by a Cu-rich highly conductive network that also possesses some degree of charge-storage capacity. This work focuses on morphological, compositional, and chemical-state distributions with submicrometer lateral resolution. This information, which is crucial because doping distribution controls supercapacitor performance, has been obtained by combining electrochemical and in situ Raman measurements with synchrotron-based X-ray fluorescence and absorption microspectroscopy. Using a microfabricated thin-layer three-electrode microcell, we followed the morphochemical changes at different electrodeposition stages and found that pulse-plating allows the growth of Mn-and Cu-doped ZnO as self-organized structures with a consistent spatially stable composition distribution.