Metal-Supported Solid Oxide Electrolysis Cells with Coatings to Suppress Chromium Migration

Abstract

High-temperature electrolysis (HTE) is an efficient technology for converting steam to hydrogen. The performance, durability, and applications of metal-supported solid oxide electrolysis cell technology developed at Lawrence Berkeley National Laboratory (LBNL) will be discussed. The unique LBNL symmetric cell architecture design, with thin zirconia ceramic backbones and electrolyte sandwiched between porous metal supports, offers a number of advantages over conventional all-ceramic cells, including low-cost structural materials (e.g. stainless steel), mechanical ruggedness, excellent tolerance to redox cycling, and extremely fast start-up capability.An inherent limitation of this design is the intimate contact between the electrode and the porous stainless steel, which is a source of chromium (Cr). Cr migrates from the support to the electrode during cell fabrication and operation, and reacts with the oxygen evolution electrocatalyst (LSCF). This Cr poisoning reduces performance and durability. To overcome this limitation, Cr-blocking coatings have been applied to the porous stainless steel. A variety of coating compositions and deposition techniques have been evaluated. The best coating dramatically reduces the amount of Cr detected in the electrode both after catalyst infiltration at 800°C and after 1000 h continuous operation at 700°C, Fig 1.Other aspects of the MS-SOEC design and operation have been optimized for performance and durability. These include the infiltrated catalyst composition and processing, metal support structure, and operating temperature. Figure 1