Electrochemical activity movies obtained by scanning electrochemical cell microscopy (SECCM) of a porous a-MoSx thin film. The dataset contains short movies denoted Movie S1-S13, consisting of independent SECCM scans on the a-MoSx film, covering homogeneous and heterogeneous areas to characterise the local structure-activity relationship with respect to total (current) and specific (current density) electrochemical activity.