Intermediate Temperature Proton-Conducting Solid Oxide Electrolysis Cells with Improved Performance and Durability

Recipient West Virginia University (PI: Xingbo Liu)

Subs Colorado School of Mines/CSM (PI: Greg Jackson)

Water Splitting Technology HTE

Status Awarded

Abstract The team will develop intermediate temperature proton-conducting solid oxide electrolysis cells (IT H-SOECs) that will operate at >1.0 A/cm2 with voltages ~1.4 V/cell at or below 600 °C which degrades ~ 4mv/1000h, and enable operational lifetimes over 40,000 h. The team will identify highly active, triple-conducting electro-catalysts and develop conformal coating methods for depositing these catalysts into composite anode functional layers to lower the dominant anode polarization resistance (Rp, anode) associated with water-splitting in H-SOECs. A significant challenge for the project lies in the identification of appropriate electro-catalyst compositions for reducing Rp,anode and then developing the fabrication methodology for incorporating the proposed surface coatings into the anode functional layers. Reducing polarization resistance will extend the active area of the anode from the surface into the bulk, maximizing conduction of protons and thus effectively splitting water.

Methods to be Employed: Optimal electro-catalyst coatings will be identified with high-throughput screening (HTS) with combinatorial coatings and E-XPS for probing local activity and overpotentials to identify preferred surface compositions for H2O splitting. An electrochemical model will be developed to investigate and validate microkinetic reaction mechanism and inform the design of cell architectures based on rate-limiting step(s) under desired high-current operating conditions. Model-informed cell design will be driven by validation with the thin-film electrode studies to assess candidate electro-catalysts and how best to integrate those materials in cell architectures that satisfy the performance targets. The H-SOEC cells will be derived from wet chemical impregnation and/or atomic layer deposition (ALD). This approach will overcome deficiencies in traditional catalyst infiltration to ensure a robust electronic/ionic pathway through the functional layer over the SOEC lifetime. These methods will be scaled up to larger-cell fabrication to promote manufacturability.

Potential Benefits and Outcomes: Key advantages of the proposed technology include:

 The H-conducting electrolyte will produce pure H2 in the Ni cathode side of the H-SOEC thus eliminating instability due to Ni oxidation common to competing technologies.

 A conformal catalyst coating optimized for H2O splitting in the anode functional layer will reduce polarization resistance as well as maintain long-term structural compatibility with the composite anode due to the matching of thermal expansion.

 The techniques for deriving the electrocatalysts and subsequent electrodes lend themselves to scale-up for manufacturability.

 The IT H-SOEC developed in the project will lower that operation temperature to ~200°C, and improve stability by ~ 5 to 8 times, as compared to state-of-art oxygen-conducting SOEC operating @ 800C, and with degradation ~ 1- 4%.