In partnership with the UK’s Carbon Trust and major automotive OEMs, ITM Power has been performing numerous standardized accelerated stress tests on its high power density membrane material (earlier post) designed to exacerbate degradation and benchmark durability. Unlike the majority of conventional fluorocarbon membrane materials which are expensive and require significant chemical plant to fabricate, ITM’s materials are low-cost hydrocarbons made by mixing together liquid chemicals to a particular recipe.
In an update, the company reports that its hydrocarbon fuel cell membrane is highly conductive and has demonstrated a high power density exceeding 1.5W/cm2 at 600mV with hydrogen/air, 0.3 mg/cm2 of platinum catalyst per electrode and low gas pressures (1.5 bar absolute).
Following achievement of these targets, ITM Power is undertaking an 18 month program focusing on membrane durability and scale-up to full automotive cell dimensions.
Three months into this program, ITM Power’s membrane material has outperformed all targets against which it has been measured. A key metric among these is voltage retention in fuel cell open circuit mode. The US Department of Energy (DOE) has established targets specifying that the cell voltage must not drop by more than 20% over 200 hours.
Using an internationally recognized and commercially available fuel cell, a membrane electrode assembly containing ITM Power’s membrane material has repeatedly shown durability beyond 700 hours (representing many 1000s of hours of normal operation). This represents more than three times the longevity specified in the DOE target, and is comparable with the best results measured for incumbent fluorocarbon membrane materials.
In addition to maintaining open circuit voltage, the membrane also measured extremely low hydrogen crossover at circa 1mA/cm2. This is close to an order of magnitude lower than that measured for incumbent fluorocarbon membrane materials.
While there are further tests yet to be conducted, ITM suggests that these early results give a positive indication of the durability offered by its fuel cell membrane against this aggressive accelerated testing.