Speaker
Description
Electrocatalytic water splitting is one of the most promising technologies for producing green hydrogen from renewable resources. However, the anodic oxygen evolution reaction (OER) remains the bottleneck of this process due to its sluggish kinetics. In alkaline water electrolysis, nanocrystalline spinel-type Co3O4 is a highly attractive anode material due to its low cost, high activity, and stability under OER conditions. It is well-established that Co-based electrocatalysts form an X-ray amorphous CoOx(OH)y surface layer under OER-relevant potentials, which can be directly linked to catalytic activity [1,2]. Despite this, the electronic and structural effects of metal dopants on the formation of the active state and the structure-activity relationships remain largely unknown.
In this work, we investigate the role of dopants in the near-surface structural and electronic transformations of metal-doped Co3-xMxO4 (M = Mn, V) nanoparticles during active state formation. Using time-resolved operando hard X-ray spectroscopies (XRD, XAS), we track the chemical and structural changes that occur during active state formation under potentiodynamic (pulsed) reaction conditions. Complementary, the oxygen evolving state is probed by soft X-ray in situ photoemission (XPS) and electron-yield X-ray absorption spectroscopy (EY-XAS).
Our findings reveal distinct structural processes arising from pseudocapacitive redox chemistry in the pre-OER region, which influence active state formation and, ultimately, catalytic turnover and stability. By integrating time-resolved structural and chemical insights, we elucidate the kinetics of processes that lead to the formation of an oxygen-evolving catalyst under operational conditions. These insights advance our understanding of key structure-activity relationships in oxygen-evolving catalysis on Co-based electrocatalysts.
Literature:
[1] Bergmann, A., Martinez-Moreno, E., Teschner, D. et al. Reversible amorphization and the catalytically active state of crystalline Co3O4 during oxygen evolution. Nat Commun 6, 8625 (2015).
[2] Tim Wiegmann, Olaf M. Magnussen et al. Operando Identification of the Reversible Skin Layer on Co3O4 as a Three-Dimensional Reaction Zone for Oxygen Evolution. ACS Catalysis 12 (6), 3256-3268 (2022).
