Augmented Stainless Steel Porous Transport Layers through Co ₃ O ₄ Spinel Deposition for the Oxygen Evolution Reaction in Alkaline Media

Glycine-nitrate autocombustion was used to synthesize stainless steel porous transport layer (PTL)-supported Co3O4-spinel particles. This composite material was employed as a platinum group metal (PGM)-free catalyst with high specific surface area and high activity for anion-exchange membrane water electrolysis (AEMWE). Significant increase of the oxygen evolution reaction (OER) activity of the PTLs was documented in a three-electrode setup, which was attributed to the combined effects of the increased specific surface area (vs the bare stainless steel PTL) and the enhanced intrinsic catalytic activity associated with the Co3O4-spinel particle deposit. The diffusion of atoms (mostly iron and nickel) arising from the PTL stainless steel fibers into the Co3O4-spinel structure enhances its mechanical stability and its OER activity. However, the formation of a thick oxide layer, especially rich in Cr, at the interface between the PTL fibers and the deposited Co3O4-spinel particles depreciates the electrode performance in single-cell AEMWE. The growth of this oxide layer, which is an intrinsic property of stainless steel, can be mitigated through the choice of refined postsynthetic heat treatment. The beneficial effect of the spinel coating on the PTLs was also confirmed under AEMWE operating conditions, underscoring its potential for integration into AEM cells, although further optimization is still warranted.