Molecular catalysis of fuel-forming half reactions such as proton and CO2 reduction is a key area of study for achieving electrical-to-chemical energy storage and solar fuel synthesis. Immobilization of these molecular catalysts on electrode surfaces often results in high turnover numbers and selectivities, even under the challenging conditions of an aqueous environment. This Perspective considers how the combination of electrochemistry and electronic spectroscopy can be used to characterize catalytic processes in operando, explaining the observed performance and therefore guiding the design principles for the next generation of material/molecule hybrid electrodes and devices. Numerous immobilization strategies and electrode materials are already available, of which wide band gap metal oxides offer transparency to visible light and are therefore ideal for spectroelectrochemical characterization. Spectroscopic analysis of emerging catalytic metal−organic framework and polymer films is also discussed.EPSRC, Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy and the National Foundation for Research, Technology and Development
