Journal
ACS CATALYSIS
Volume 5, Issue 11, Pages 6600-6607Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.5b01779
Keywords
electrocatalysis; oxygen reduction reaction; lithium-oxygen; water networks; batteries; activated water
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Funding
- Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub - U.S. Department of Energy, Office of Science, Basic Energy Sciences
- Argonne, a U.S. Department of Energy Office of Science laboratory [DE-AC02-06CH11357]
- U.S. Department of Energy, Basic Energy Science, Materials Science and Engineering Division
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Water and oxygen electrochemistry lies at the heart of interfacial processes controlling energy transformations in fuel cells, electrolyzers, and batteries. Here, by comparing results for the ORR obtained in alkaline aqueous media to those obtained in ultradry organic electrolytes with known amounts of H2O added intentionally, we propose a new rationale in which water itself plays an important role in determining the reaction kinetics. This effect derives from the formation of HOad center dot center dot center dot H2O (aqueous solutions) and LiO2 center dot center dot center dot H2O (organic solvents) complexes that place water in a configurationally favorable position for proton transfer to weakly adsorbed intermediates. We also find that, even at low concentrations (<10 ppm), water acts simultaneously as a promoter and as a catalyst in the production of Li2O2, regenerating itself through a sequence of steps that include the formation and recombination of H+ and OH-. We conclude that, although the binding energy between metal surfaces and oxygen intermediates is an important descriptor in electrocatalysis, understanding the role of water as a proton-donor reactant may explain many anomalous features in electrocatalysis at metal-liquid interfaces.
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