Pure Hydrogen Production Through Precious-Metal Free Membrane Electrolysis of Dirty Water
Recipient University of Oregon (PI: Shannon Boettcher)
Water Splitting Technology LTE
Abstract Water electrolysis with conventional membrane electrolyzers (e.g. using a proton-exchange membrane, PEM, such as Nafion) use ultra-pure water to avoid fouling the membrane and electrode catalysts. They also use rare and expensive precious-metal catalysts. The use of ultrapure water increases system capital/maintenance cost, complexity and size. The use of precious metals limits scalability and increases cost. If equivalent performance and lifetime could be achieved using an alternative approach that could directly utilize, without purification, “dirty” water (for example, greywater or seawater) as well as all non-precious-metal catalysts and, ideally, inexpensive hydrocarbon membranes, it would significantly decreases capital costs and thus increase the market penetration of H2 production technology. A better understanding of degradation mechanisms and how to prevent them would also help improve current technology.
The key objective of the proposed work is to advance the understanding of, and develop mitigation strategies for, the negative effects of using low-purity feed water in membrane electrolyzers. The project thus spans device development and advanced analysis using electrochemical measurement, modelling, and cross-sectional nanoscale morphology / chemical analysis using focused-ion-beam milling and electron microscopy. Feed water with controlled impurity content will be tested to assess the role of each degradation mechanism. Based on this foundational knowledge, we will develop electrolyzers fed by unpurified water using anion-exchange membranes (AEMs) and/or bipolar membranes (BPMs) where we control the local reaction pH and the flow of particular ions and water across the membrane(s) to prevent fouling. Combined with judiciously designed oxygen-evolution reaction (OER) and hydrogen-evolution reaction (HER) electrocatalysts, high-performance and practical long-term durability may be possible during the electrolysis of dirty greywater and/or seawater.