Engineering Fuel Cell Electrodes to Overcome Ion Transport Limitations using Low-cost, Efficient Lignin-based Ionomers

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Eco-friendly, affordable technologies for electric cars are needed to reduce greenhouse gas emissions. One promising solution is the proton exchange membrane fuel cell (PEMFC), an electrochemical technology that uses hydrogen as fuel. However, current PEMFCs use an ion-conducting polymer, called Nafion which is expensive and not eco-friendly. Most importantly, Nafion fails to transport protons efficiently in thin layers (coating the catalyst and electrode) which negatively impacts PEMFC performance and limits real world applicability. This project aims to address these cost, performance, and environmental concerns by using a new class of eco-friendly, efficient ion-conducting polymers. These polymers will be derived from lignin, the second most naturally abundant polymer that is found in plant cell walls and a waste byproduct of agricultural farms, pulp and paper industries, and biorefineries. In this project, the PI will use lignin from plant sources to make ion-conducting polymers and examine their ability to transport protons in thin layers and interfaces, such as those found in PEMFCs. This project is the first step to enable lignin-based ion-conducting polymers to replace Nafion, make PEMFC vehicles efficient and cost competitive to battery-powered vehicles. This project will introduce the energy research community to a new concept “Green Energy using Green Materials” and enable training of graduate, undergraduate, and high school students for a future diversified energy workforce. The research will also be complemented by data-driven outreach programs to support energy literacy across Nebraska, integrate gamification into courses to stimulate student critical thinking, engage K-12 students and the general public to broaden STEM participation, and facilitate energy education for people of all ages. The goal of this project is to overcome ion transport limitation, a major scientific challenge limiting the adoption of proton exchange membrane fuel cells (PEMFCs), by utilizing lignin-derived ionomers. The project will investigate how to boost interfacial ion transport by using lignin-based ionomers and manipulating the chemical, molecular, and orientational landscape next to the substrate of sub-micron-thick ionomer layers. The project will open new pathways to expedite interfacial electrochemical processes by (1) elucidating interfacial proton transport properties within thin films and catalyst layer mimicking systems made of a series of lignin-based ionomers; (2) engineering the interface using lignin-based ionomers to reveal their role on depth-specific ion transport properties; and (3) examining how proton transport in lignosulfonic acid ionomer-based electrode-mimicking thin systems is controlled by interfacial wetting, chemical composition, ionic domain characteristics, nanostructure, and viscoelastic properties. The gained knowledge will pave new ways to understand and expedite interfacial electrochemical processes, empower the design of cost-effective, eco-friendly, and efficient energy conversion/storage devices, promote innovative ways to valorize the neglected biomass lignin, and aid in both bio- and energy economy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.