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

Abstract

• Evaluation of cobalt oxide-based materials as cathode catalyst in PEM electrolyzer. • Optimum amount of carbon additive results in high performance. • Co 3 O 4 -based catalyst outperforms Pt at high cell potentials. • In situ XAS of Co 3 O 4 -electrode catalysts under PEM electrolysis conditions. • Dynamic changes of Co 2+ /Co 3+ fractions with temperature and applied potential. 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, Co 3 O 4 and MoS 2 ) revealed that better performance was attained with Co 3 O 4 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 47 wt% Co 3 O 4 over the total amount. At 2.05 V, 47 wt% Co 3 O 4 -based catalyst (0.55 A/cm 2 ) outperformed 47 wt% MoS 2 -based one (0.51 A/cm 2 ). More importantly, the performance of the former at 2.3 V (1.12 A/cm 2 ) surpassed even that of Pt-black (1.11 A/cm 2 ). In situ XAS study of the Co 3 O 4 -based material under PEM electrolysis conditions revealed dynamic interchange of Co 3+ and Co 2+ fractions, which was attributed to ultimately boost the HER performance.