Influence of Annealing Temperature on the OER Activity of NiO(111) Nanosheets Prepared via Microwave and Solvothermal Synthesis Approaches
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- Carl von Ossietzky University of Oldenburg (Germany)
- Colorado School of Mines, Golden, CO (United States)
- Carl von Ossietzky University of Oldenburg (Germany); German Aerospace Center (DLR), Oldenburg (Germany)
- German Aerospace Center (DLR), Oldenburg (Germany)
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (Germany)
- Colorado School of Mines, Golden, CO (United States); National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Earth-abundant transition metal oxides are promising alternatives to precious metal oxides as electrocatalysts for the oxygen evolution reaction (OER) and are intensively investigated for alkaline water electrolysis. OER electrocatalysis, like most other catalytic reactions, is surface-initiated, and the catalyst performance is fundamentally determined by the surface properties. Most transition metal oxide catalysts show OER activities that depend on the predominantly exposed crystal facets/surface structure. Therefore, the design of synthetic strategies to obtain the most active crystal facets is of significant research interest. In this work, rock salt NiO OER catalysts with (111) predominantly exposed facets were synthesized by a solvothermal (ST) method either heated under supercritical or microwave-assisted (MW) conditions. Particular emphasis was placed on the influence of the post annealing temperature on the structural configuration and OER activity to compare their catalytic performances. The as-prepared electrocatalysts are pure α-Ni hydroxides which were converted to rock salt NiO (111) nanosheets with hexagonal pores after heat treatment at different temperatures. The OER activity of the electrodes has been evaluated in 0.1 M KOH using geometric and intrinsic current densities via normalization by the disk area and BET area, respectively. The lowest overpotential at a geometric current density of 10 mA/cm2 is found for samples pretreated by heating between 400 and 500 °C with a catalyst loading of 115 μg/cm2. Despite the very similar nature of the catalysts obtained from the two methods, the ST electrodes show a higher geometric and intrinsic current density for 500 °C pretreatment. The MW electrodes, however, achieve an optimal geometric current density for 400 °C pretreatment, while their intrinsic current density requires pretreatment over 600 °C. Interestingly, pretreated electrodes show consistently higher OER activity as compared to the poorly crystalline/less ordered hydroxide as-prepared electrocatalysts. Thus, our study highlights the importance of the synthesis method and pretreatment at an optimal temperature.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); German Research Foundation (DFG); USDOE
- Grant/Contract Number:
- AC36-08GO28308
- OSTI ID:
- 2477751
- Report Number(s):
- NREL/JA--2800-92121; MainId:93899; UUID:a33bb339-7773-4ed2-b0c6-f42ee04913aa; MainAdminId:74281
- Journal Information:
- ACS Applied Materials and Interfaces, Journal Name: ACS Applied Materials and Interfaces Journal Issue: 45 Vol. 16; ISSN 1944-8244
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
electrical properties
electrocatalysts
electrodes
electrolysis
facet control
microwave synthesis
oxides
oxygen evolution reaction (OER)
radiology
rock salt
supercritical solvent
surface termination
two dimensional materials