Isotope-Labeling Studies in Electrocatalysis for Renewable Energy Conversion

• Main Author: Scott, Søren Bertelsen
• Format: Book
• Language: English
• Published: Technical University of Denmark 2019
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/affordable_and_clean_energy; SDG 7 - Affordable and Clean Energy; /dk/atira/pure/sustainabledevelopmentgoals/climate_action; SDG 13 - Climate Action; Carbonic acid
• Online Access: https://orbit.dtu.dk/en/publications/eb178af3-8f48-4a1d-8cc0-587552d0e94b; https://backend.orbit.dtu.dk/ws/files/195825088/S_ren_Bertelsen_Scott.pdf

This thesis presents methods and results for isotope-labeling studies in oxygen evolution reaction (OER) electrocatalysis. The OER is an essential reaction for a transition to a fossil-fuel-free society. The OER is the main source of e ciency loss in the production of hydrogen by water electrolysis. Hydrogen from water electrolysis, in turn, is key for storing wind and solar energy and for using wind and solar electricity to decarbonize other sectors such as industry and transport. The rst chapter of this Thesis puts this technological motivation in the context of the urgent need to mitigate climate change. The second chapter describes and demonstrates the tools used in the isotope-labeling electrocatalysis studies. The primary tool is electrochemistry-mass spectrometry (ECMS). The version of EC-MS used in this Thesis involves a silicon microchip to make the interface between the high vacuum of the mass spectrometer and the wet ambient environment of the electrochemistry experiment. The advantages of this technique, chip EC-MS, are high sensitivity, well-characterized mass transport, and the ability to dose reactant gases. Isotope labeling studies are introduced with two examples. The rst is an attempt to directly measure the hydrogen evolution exchange current density on platinum by electrochemical H-D exchange, which is however demonstrated to be mass-transport limited. The second is a set of CO stripping and CO oxidation experiments in labeled electrolyte (H 2 18 O), which lead to a new way to probe the kinetics of the reaction of CO 2 and H 2 O to form carbonic acid. The third chapter is devoted to oxygen evolution electrocatalysis. The two main water electrolyzers, alkaline electrolyzer cells (AEC) and polymer electrolyte membrane electrolyzer cels (PEMEC), are brie y discussed in the context of the OER catalysts required. Then, the importance of measuring O 2 is demonstrated with two examples in which the electrochemical current would overestimate the OER activity. This motivates the study with EC-MS of ...