In-depth cyclic voltammetry analysis has proven to be a powerful tool for addressing intricate reaction mechanisms involving proton-coupled electron transfer (PCET) reactions.1 We have demonstrated the use of this analytical technique to study intramolecular PCET reactions,2 molecular bond breaking coupled with PCET reactions,3 molecular catalytic reactions coupled with PCET,4 and heterogeneous electrocatalyst mechanisms involving PCET.5 These fundamental reactions are illustrated through theoretical analysis and experimental examples. Electrochemical water splitting is a clean technology with the potential for large-scale production of highly pure dihydrogen, a major energy vector for the near future. Over the years, benchmarking protocols have been proposed to evaluate the electrocatalytic water splitting activity and stability of heterogeneous hydrogen and oxygen evolution reaction electrocatalysts. However, the complexity of these multiple electron/proton transfer reactions makes it difficult to obtain reliable electrochemical measurements and gain direct insight into the HER and OER mechanisms. Herein we will discuss different aspects of PCET reactions, from electrochemical water splitting toward lignin activation. 1. a) Bonin, J.; et al. C. Acc. Chem. Res. 2012, 45, 372; b) Costentin, C.; et al. Acc. Chem. Res. 2014, 47, 271. 2. Costentin, C.; et al. Angew. Chem. Int. Ed. 2010, 49, 3803. 3. a) Costentin, C.; et al. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 8559; b) Savéant, J.-M.; Tard, C. J. Am. Chem. Soc. 2014, 136, 8907. 4. a) Savéant, J.-M.; Tard, C. J. Am. Chem. Soc. 2016, 138, 1017; b) Costentin, C.; Savéant, J.-M.; Tard, C. ACS Energy Lett. 2018, 3, 695. 5. Costentin, C.; et al. C. Nat. Mat. 2017, 16, 1016. 6. a) Faustini, M.; et al. Adv. Energy Mater. 2019, 9, 1802136; b) Elmaalouf, M; et al. Nat. Commun. 2021, 12, 3935. c) Elmaalouf, M.; et al. Chem. Sci. 2022, 13, 11807.