Dubai, Erik ; Wu, Qingyang ; Lauterbach, Stefan ; Hofmann, Jan P. ; Einert, Marcus (2024)
Surface defects, Ni3+ species, charge transfer resistance, and surface area dictate the oxygen evolution reaction activity of mesoporous NiCo2O4 thin films.
In: ChemNanoMat, 10 (11)
doi: 10.1002/cnma.202400242
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

For catalyzing the oxygen evolution reaction, earth‐abundant materials with high activity and stability need to be developed. NiCo 2 O 4 has been proven to show high OER activity, however facile and inexpensive techniques for preparation of this compound as mesostructured thin film, possessing a high surface area, is lacking. In this study, the sol‐gel synthesis of nanocrystalline, mesoporous spinel NiCo 2 O 4 thin films by dip‐coating and soft‐templating using the evaporation‐induced self‐assembly approach and utilizing the tri‐block‐copolymer Pluronic® F‐127 as structure‐directing agent is reported. The morphology and crystallographic structure were thoroughly probed by various physicochemical characterization techniques collectively validating the development of uniform mesoporous NiCo 2 O 4 architectures crystallizing exclusively in the cubic spinel phase after calcination in air at ether 300 °C, 400 °C, or 500 °C. The surface area of thin films increased from 300 °C to 400 °C owing to degradation of the organic template, while the growth of the mesopores from 400 °C to 500 °C resulted in significant decline of the overall (electrochemical) surface area. XPS investigations showed that the amount of octahedrally coordinated Ni 3+ and defective (low‐coordinated) oxygen species increased for decreasing calcination temperatures. The nanomorphology and presence of catalytically active surface sites of the mesoporous NiCo 2 O 4 electrodes were correlated with the electrochemical properties, presenting that the overall surface area, Ni 3+ content, charge transfer resistance, and amount of defective oxygen sites collectively control the OER performance. After an optimized annealing procedure at 300 °C and chronopotentiometric analysis at 10 mA/cm 2 for 1.5 h, a low overpotential of 330 mV vs. RHE at 10 mA/cm 2 in alkaline solution was achieved. The results highlight the necessity of precise selection of the appropriate calcination temperature and tailoring of the nanostructure and electrochemical pre‐treatment conditions of NiCo 2 O 4 sol‐gel thin films for adjusting the concentration of electrocatalytically active reaction sites.

Frage zum Eintrag

Redaktionelle Details anzeigen