In situ study of copper electrodeposition on a single carbon fiber

► Wet electrochemical process was studied by in situ X-ray diffraction and fluorescence technique. ► An electrochemical cell was specially designed for in situ study. ► Quantitatively controlled Cu electrodeposition on single carbon fiber. ► Nanoscale nucleation and growth of Cu electrodeposition was studied by SEM. ► A transition of reaction controlled process to diffusion controlled process was revealed.