Hydrogen production via electrolysis: Operando monitoring and analyses

For deep decarbonization, pressure is on to develop better green hydrogen energy sources with higher efficiency, extended durability, and lower cost. Electrolysis is very promising for green hydrogen production, yet several challenges need to be overcome. Operando techniques can offer in situ monitoring and real-time observation of water electrolysis, including reaction mechanisms, structural changes, ionic conductivity, transport properties, and degradation mechanisms. We first discuss the current progress in operando analysis of electrolysis for hydrogen production and provide an overview of recent advances in radiography and tomography techniques: infrared, Raman, X-ray absorption, photoelectron, and electrochemical impedance spectroscopy methods. Next, operational principles; temporal, spatial, and spectral ranges; and limitations in operando monitoring and analyses are presented. Furthermore, reactions and mechanisms that occur in these systems, and resultant system durability, are reviewed. Finally, we recommend future directions in operando characterization for enhancing live monitoring of reactions, transport phenomena, and degradation mechanisms in hydrogen production.