Cobalt oxide-based materials as non-PGM catalyst for HER in PEM electrolysis and in situ XAS characterization of its functional state

Abstract

The polymer electrolyte membrane (PEM)-based electrolysis technology is a promising mean to split water and store renewable energy in the form of clean fuel, hydrogen. However, its high price due to the use of platinum group metals (PGMs) as catalyst materials generally makes the technology cost-restrictive. Herein we present the performance evaluation of cobalt oxide in PEM electrolysis as cathode catalyst where hydrogen evolution reaction (HER) takes place. Performance comparison of non-PGM catalysts (CoO, Co3O4 and MoS2) revealed that better performance was attained with Co3O4 and it was further improved by mixing with an electrically conducting carbon material (Vulcan). An optimum amount of the carbon additive was found, and the best performance was recorded at 47wt% Co3O4 over the total amount. At 2.05 V, 47wt% Co3O4-based catalyst (0.55 A/cm2) outperformed 47wt% MoS2-based one (0.51 A/cm2). More importantly, the performance of the former at 2.3 V (1.12 A/cm2) surpassed even that of Pt-black (1.11 A/cm2). In situ XAS study of the Co3O4-based material under PEM electrolysis conditions revealed dynamic interchange of Co3+ and Co2+ fractions, which was attributed to ultimately boost the HER performance.