Electrochemical energy conversion devices such as fuel cells, water electrolyzers and electrochemical synthesis reactors play a critical role in reducing global dependence on fossil fuels and promoting renewable hydrogen technology as a path to industrial decarbonization. While significant progress has been made in the development of PGM and PGM-free catalysts for oxygen reduction and evolution, hydrogen oxidation and evolution, and CO2 reduction and valorization, there are missing links between the materials synthesis evaluation on one side, and modeling and characterization on the other. This workshop aims to facilitate discussions on the key functional characteristics of catalysts and explore how these can be characterized. We will discuss the development of best practices and protocols, including accelerated stress tests, improved electrochemical diagnostics, and innovative physicochemical characterization methods. Of special interest are in situ and operando methods, as well as advances in microscopy, spectroscopy or tomography techniques and novel approaches that have yet to be widely adopted. This discussion will be complemented by modeling of catalysts structure-to-reactivity features focusing on reaction mechanisms, stability and degradation investigations, and catalyst integration with other components of the electrochemical devices.