A novel combination of Surface X-ray Scattering techniques (SXS), i. e. GISAXS (Grazing-Incidence Small-Angle X-Ray Scattering), XRR (X-Ray Reflectivity) and SXRD (Surface X-Ray Diffraction) alongside with simultaneous detection of gaseous products by OLEMS (On-Line Electrochemical Mass Spectrometry) has been applied to study under operando conditions structure-activity relationships of a Pt model electrocatalyst. The SXS-OLEMS combination is able to follow dynamic changes in surface morphology and crystallography during water electrolysis. To showcase the combined SXS-OLEMS setup for operando studies of electrode transformations, H₂ and O₂ evolution reactions (HER and OER) on a Pt model electrocatalyst and their dependence on type and degree of surface roughening have been investigated.