Insights into the electrochemical redox mechanisms of copper in alkaline solution with digital holography and SECM

In this study, in situ digital holography combined with scanning electrochemical microscopy (SECM) was employed to systematically investigate the multi-step electrochemical reaction mechanisms of copper in alkaline solution. The results demonstrate that the anodic oxidation exhibits two characteristic peaks. The first peak corresponds to the solid-phase transformation of Cu to Cu 2 O via a Cu(OH) intermediate, accompanied by the formation of small amounts of soluble Cu(I) species. The second peak initially involves active dissolution generating soluble Cu(II), followed by the formation of a dense Cu(OH) 2 /CuO passive film. The cathodic reduction also displays two characteristic peaks, assigned to the stepwise solid-phase reduction of Cu 2 O and CuO/Cu(OH) 2 , during which OH − is released, with negligible diffusion of soluble copper species. This work presents the first in situ combination of digital holography with SECM, enabling simultaneous tracking of electrochemical signals, interfacial concentration variations, and localized active species. The kinetic differences among individual reaction steps and the dynamic coupling mechanism between solid and liquid phases products are elucidated.