Foundational Science for Robust Bipolar-Membrane Electrolyzers for O2 Generation from Seawater at High Rate and Efficiency Objective
Abstract
While traditional membrane electrolyzers rely on ultrapure water feeds to generate H2 and O2, direct electrolysis of impure water sources, e.g. seawater, could have some advantages, enabling broader access to water feedstocks. This path can reduce capital costs by mitigating the need for on-site water purification and could enable smaller-scale mobile electrolyzer architectures also appropriate for space constraints on submarines or for underwater life support to generate breathable O2 on demand. However, electrolyzing seawater or other water sources with impurities to generate H2 and O2 introduces significant challenges in comparison to electrolyzing ultrapure water. One challenge arises from the high concentrations of ionic species (e.g., Cl-, Na+, SO42-, Mg2+, Ca2+, etc.) # particularly Cl- # in seawater. The Cl- oxidation reaction generates corrosive #free chlorine# species (i.e., Cl2, HOCl, OCl-) at the electrolyzer anode posing significant challenges to the safety, efficiency, and durability of seawater electrolyzers during operation. Mitigating the Cl- oxidation reaction with impure water feed also opens the possibility of making use of a pure O2 stream from the anode for uses including undersea operations and life-support. More broadly, the development of high-performance, compact electrolyzer platforms that tolerate operation on water from a broad array of sources durably, without risk of failure, could have applications in H2 fuel production for Navy, Army, or Airforce applications, particularly where space, weight, and system complexity are key limiting factors such as at forward operating bases. Bipolar membrane water electrolyzers (BPMWEs) are a new technology, invented by PI Boettcher that provide a new and promising route to meet these Department of Defense application targets. In this proposal, Boettcher (University of Oregon) and Jaramillo and Nielander (Stanford University) will collaborate to address the following key aims. Aim 1: Understand the fundamental mechanisms by which different and common seawater constituent ions Na+, Mg2+, Cl-, SO42-, etc., interact with electrolyzer components and modulate rate processes that control performance and durability of seawater BPMWEs. Aim 2: Measure and control the fundamental parameters and processes that control ionomer adhesion at catalyzed bipolar membrane interface in seawater and impure water sources. Aim 3: Design further-improved water-dissociation catalyst layers to enable >2 A cm-2 bipolar membrane electrolyzers in impure and seawaters without increasing voltage loss. Aim 4: Define the processes that control the anode-membrane interface selectivity for oxygen evolution to suppress the degradation processes with impure water feed. Approved for Public Release.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 11, 2023
- Source ID
- N000142312820
Entities
People
- Shannon W. Boettcher
Organizations
- Office of Naval Research
- United States Navy
- University of Oregon