PGM-free OER Catalysts for PEM Electrolyzer

Recipient Argonne National Laboratory/ANL (PI: Di-Jia Liu)

Subs University of Buffalo (PI: Gang Wu) and Giner (PI: Hui Xu)

Water Splitting Technology LTE

Status Awarded

Abstract Low temperature water electrolysis represents one of the critical technologies in distributed hydrogen production. It produces clean hydrogen with fast response time and works perfectly when coupled with renewable but intermittent power sources such as wind and solar. Low temperature electrolyzer can be operated by using either proton or anionic exchange membrane. Compared to its alkaline counterpart, proton exchange membrane (PEM) electrolyzer offers many advantages including significantly higher current density (x5 improvement) and higher H2 purity, rendering it a preferred technology when high efficiency and low footprint are essential. The benefits of PEM electrolyzer are attributed to its high ion conducting membrane. Working in the oxidative and acidic environment under high polarization voltage, however, adds substantial challenges to the electrode catalyst activity and durability. This is particularly the case at anode where the oxygen evolution reaction (OER) takes place which demands more catalyst due to its higher overpotential. At present, the platinum group metal (PGM) materials such as iridium black are the catalysts of choice. Their high cost and limited reserve, however, pose significant barriers to widespread implementation of PEM electrolyzer in the renewable energy landscape. Low-cost transition metals and their oxides are known to be active toward the OER in alkaline electrolyte but unstable in acid. Furthermore, traditional carbon as the catalyst support cannot sustain the oxidative potential during the OER before being oxidized to CO2.

To address the grand challenges of material cost, activity and stability, this proposal focuses on developing the next-generation, high-efficiency and durable PGM-free OER catalysts for the PEM electrolyzer. It is based on the initial successes developed at our laboratories. The new catalysts are composed of porous yet stable transition metal carbonitrides incorporated in a 3-D nano-network electrode architecture. The new catalysts are projected to be low-cost, highly conductive and active toward OER yet resistant to the oxidation corrosion. Our goal is to produce one or more PGM-free OER catalysts with the performance approaching to the current Ir catalyst at < 1/20 of the cost, demonstrated in the operating PEM electrolyzer. Our ultimate objective is to reduce the PEM electrolyzer capital cost in meeting the DOE hydrogen production price target of $2 / kg H2 while maintaining the system efficiency at 43 kWh/kg H2.