Oxygen Generation and Extraction from Seawater
Abstract
Human performance in maritime operations requires the availability of oxygen. This proposal seeks to provide the basic science needed for using seawater as a source of oxygen. There are two sources of oxygen in the sea: dissolved oxygen and oxygen that is available from the electrolysis of seawater. For either case, the most basic science issues of obtaining oxygen from seawater havenot yet been solved. Can oxygen be produced selectively from seawater without the need for prepurification steps? This proposal seeks to address this question by exploring the basic science behind producing oxygen from an ocean environment by two methods: (i) water electrolysis and (ii) extraction. Specific objectives of the proposal for water electrolysis are to use differentialelectrochemical mass spectrometry to assess the overpotentials for water versus halide oxidation. The assay will allow a quantitative readout for determining faradaic efficiency and thus selectivity of oxygen evolution catalysis from seawater versus other oxidations such as organics and salts.Metal oxygen evolving catalysts, M-OECs, will self-heal themselves during catalytic operation. The self-healing properties of these catalysts will be examined to assess their ability to perform electrolysis from a natural water source such as seawater. Critical to the function of the system will be the ability to fabricate M-OECs that are able to minimize the overpotential for oxygengeneration from water splitting and maximize the overpotential for halide oxidation to halogens/hypohalous acids. Accordingly, mixed metal OECs will be explored in which oxygen evolution activity may be optimized independently from catalyst stability. We propose using structural metals to stabilize an oxide framework that houses catalytic metals. In this manner, the proton-coupled electron transfer chemistry of water splitting may be enhanced by tuning metals,while preserving stable catalyst operation. Attention will be also directed toward extracting oxygen from seawater by taking inspiration from nature and designing a system reminiscent of the equilibrium that Nature uses for oxygen extraction. The specific objective will be to exploit the Mn+???oxygen ??? Mn+1???superoxide equilibrium to bind oxygen from seawater and then upon application of a small potential, release that bound oxygen into a pure, breathable stream.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 27, 2018
- Source ID
- N000141812650
Entities
People
- Dan Nocera
Organizations
- Office of Naval Research
- President and Fellows of Harvard College
- United States Navy