Hydroxide Ion Exchange Polymers
Hydrogen is a valuable energy carrier that is widely used at present in the chemical industry. As a fuel, it has the potential to play a key role in enabling emission-free transportation. Hydrogen can be used to power a vehicle with a fuel cell, which emits only water and can fully recharge for a 300-mile range in minutes, similar to gasoline vehicles. However, mass adoption of fuel cell vehicles has been hampered by high prices largely attributed to the cost of the proton exchange membrane (PEM) fuel cell system that is commonly used. While significant technical progress has been made in the development of acidic PEM fuel cells, a key barrier is the need to use platinum catalysts for the reactions, which are both costly and limited in abundance. In addition, at current low volumes, the acidic membranes are costly. An alternative path is to develop alkaline membranes that have the potential to both eliminate the need for expensive catalysts, and also produced at lower cost and volumes. The alkaline pathway is also promising for the development of electrolyzers that split water into hydrogen and oxygen. The hydrogen can be used in current industrial processes such as ammonia production or in other applications, such as fuel cell vehicles or as storage for intermittent electricity generation. Eliminating expensive catalysts and lowering membrane costs will help reduce capital costs for electrolyzers, hastening their widespread use.
Project Innovation + Advantages:
Rensselaer Polytechnic Institute (RPI) will develop hydroxide ion-conducting polymers that are chemically and mechanically stable for use in anion exchange membranes (AEM). Unlike PEMs, AEMs can be used in an alkaline environment and can use inexpensive, non-precious metal catalysts such as nickel. Simultaneously achieving high ion conductivity and mechanical stability has been a challenge because high ion exchange capacity causes swelling, which degrades the system’s mechanical strength. To solve this problem, the team plans to decouple the structural units of the AEM that are responsible for ion conduction and mechanical properties, so that each can contribute to the overall properties of the AEM. The team will also use channel engineering to provide a direct path for ion transport, with minimal room for water, in order to achieve high ion conductivity with low swelling. If successful, the team hopes to create a pathway to the first commercial hydroxide ion exchange membrane products suitable for electrochemical energy conversion technologies.
If successful, developments made under the IONICS program will create a fundamentally lower cost trajectory for electrochemical systems, such as fuel cells and electrolyzers, which are currently based on proton exchange membranes.
IONICS program innovations could contribute to energy storage and conversion solutions for transportation and the grid, lessening U.S. dependence on imported oil and improving grid resilience.
Greater integration of renewable resources into the power mix will reduce the need for other more carbon-intensive forms of electricity generation.
IONICS program innovations could permit the use of the oxygen and hydrogen electrodes with low-cost catalysts and other components, which could save over 50% of current fuel cell stack costs (at high volume) and reduce vehicle fuel cell system and combined heat and power system costs by about 25%.