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Abstract NiOxnanocatalysts with two distinct morphologies, nano-spindles and nano-plates, were synthesized and evaluated for oxygen evolution reaction (OER) performance. Spindle-like NiOxwas preparedviaa hydrothermal reaction of nickel nitrate and urea with cetyltrimethylammonium bromide as a surfactant at 120 °C for 24 h, forming Ni(OH)2-based intermediates that were subsequently calcined at 300 °C for 3 h. In contrast, platelet-like Ni(OH)2nanocrystals were obtained using nickel(II) acetate and KOH at 180 °C for 24 h, followed by calcination at 400 °C or 500 °C for 4 h to yield NiOxnano-plates. The NiOxnano-spindles exhibited an OER overpotential of 395 mV at 10 mA/cm2, whereas the NiOxnano-plates annealed at 400 °C and 500 °C showed overpotentials of 565 mV and 474 mV at 10 mA/cm2, respectively. Structural characterization and X-ray photoemission spectroscopy indicate these differences arise from morphology-dependent surface structures that govern catalytic activity. Graphical abstract
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Structural identification of disordered γ-MnOOH in the alkaline MnO2 discharge mechanism
Abstract The alkaline battery MnO2discharge mechanism progresses from tunneled γ-MnO2to tunneled α-MnOOH to layered Mn(OH)2as the reduction proceeds from charged Mn(IV) to discharged Mn(II). However, the existence of a disordered intermediate has recently been suggested in the “second electron” region between Mn(III) and Mn(II). The authors useoperandoextended X-ray absorption fine structure (EXAFS) to observe the structural evolution. A disordered γ-MnOOH was identified, which was the majority material for a substantial period before the sudden appearance of Mn(OH)2in the final moments of discharge. In rechargeable Bi-modified electrodes, the disordered γ-MnOOH was more efficiently converted to Mn(OH)2. Graphical abstract
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- Award ID(s):
- 2044602
- PAR ID:
- 10685957
- Publisher / Repository:
- Materials Research Society
- Date Published:
- Journal Name:
- MRS Communications
- Volume:
- 15
- Issue:
- 4
- ISSN:
- 2159-6867
- Page Range / eLocation ID:
- 697 to 704
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1557/s43579-025-00743-8
