The successful deployment of alternative energy sources that are required to ensure a sustainable future based on clean energy production and consumption depends critically on the development of materials that can efficiently transform electrical energy in chemical bonds. Water electrolysis is a fundamental process to achieve abundant hydrogen production, but currently is highly dependent on precious metals as catalysts for the Hydrogen Evolution Reaction (HER). The use of cost-effective materials such as MoS₂ and Mo-based chalcogels provide a unique catalytic opportunity to replace Pt, but that may suffer at the expense of lower conductivity and form the stability of their surfaces. Therefore, understanding the links between activity and stability on cost effective materials is critical to the development of more active and stable catalysts. In order to do so our approach employs the Stationary Probe Rotating Disk Electrode (SPRDE) connected to an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) that allows simultaneous measurement of dissolution of Mo and S atoms while HER is taking place. The insights gained with SPRDE-ICP-MS reveals an unexpected element dependent dissolution profile during HER that shed a different light on the nature of active sites and how stability plays a key role in it. The addition of dopant elements such as Ni, Co and Fe provide a framework on how all elements together alter the activity-stability relationships, guiding us on designing the next generation of catalysts.