The concept of solid catalysts with ionic liquid layer (SCILL) originates from the field of heterogeneous catalysis, where it offers a unique way to regulate both the catalytic activity and selectivity. In the past decade, applying this concept in electrocatalysis represented a new, exciting, and growing research field to influence the active sites microenvironment. The insights obtained for application of the SCILL concept for platinum-based oxygen reduction catalyst will be reviewed. This includes the importance of catalyst testing under technical relevant conditions and the method developments for testing catalysts in gas-diffusion electrode half-cells under high current densities. Furthermore, insight into the restructuring of PtNiMo/C catalysts during preconditioning with slow scan rates, leading to higher steady state activities, and the influence of ILs on this restructuring will be presented.