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Title: Water as a promoter and catalyst for dioxygen electrochemistry in aqueous and organic media.

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.
Authors:
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Publication Date:
OSTI Identifier:
1223600
Report Number(s):
SAND-2014-18453J
Journal ID: ISSN 2155-5435; 125590
Grant/Contract Number:
AC02-06CH11357; AC04-94AL85000
Type:
Published Article
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 5; Journal Issue: 11; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
batteries; lithium-oxygen; oxygen reduction reaction; activated water; electrocatalysis; water networks; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; lithium−oxygen