In this work, an organic‐inorganic hybrid crystal, violet‐crystal (VC), was used to etch the nickel foam (NF) to fabricate a self‐standing electrode for the water oxidation reaction. The efficacy of VC‐assisted etching manifests the promising electrochemical performance towards the oxygen evolution reaction (OER), requiring only ~356 and ~376 mV overpotentials to reach 50 and 100 mA cm−2, respectively. The OER activity improvement is attributed to the collectively exhaustive effects arising from the incorporation of various elements in the NF, and the enhancement of active site density. Furthermore, the self‐standing electrode is robust, exhibiting a stable OER activity after 4,000 cyclic voltammetry cycles, and ~50 h. The anodic transfer coefficients (
This content will become publicly available on June 1, 2024
- Award ID(s):
- 2055257
- NSF-PAR ID:
- 10435521
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 170
- Issue:
- 6
- ISSN:
- 0013-4651
- Page Range / eLocation ID:
- 066502
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract α a) show that the first electron transfer step is the rate‐determining step on the surface of NF‐VCs‐1.0 (NF etched by 1 g of VCs) electrode, while the chemical step involving dissociation following the first electron transfer step is identified as the rate‐limiting step in other electrodes. The lowest Tafel slope value observed in the NF‐VCs‐1.0 electrode indicates the high surface coverage of oxygen intermediates and more favorable OER reaction kinetics, as confirmed by high interfacial chemical capacitance and low charge transport/interfacial resistance. This work demonstrates the importance of VCs‐assisted etching of NF to activate the OER, and the ability to predict reaction kinetics and rate‐limiting step based onα avalues, which will open new avenues to identify advanced electrocatalysts for the water oxidation reaction. -
null (Ed.)Nickel nitride (Ni 3 N) is known as one of the promising precatalysts for the electrochemical oxygen evolution reaction (OER) under alkaline conditions. Due to its relatively low oxidation resistance, Ni 3 N is electrochemically self-oxidized into nickel oxides/oxyhydroxides (electroactive sites) during the OER. However, we lack a full understanding of the effects of Ni 3 N self-oxidation and Fe impurity incorporation into Ni 3 N from electrolyte towards OER activity. Here, we report on our examination of the compositional and structural transformation of Ni 3 N precatalyst layers on Ni foams (Ni 3 N/Ni foam) during extended periods of OER testing in Fe-purified and unpurified KOH media using both a standard three-electrode cell and a flow cell, and discuss their electrocatalytic properties. After the OER tests in both KOH media, the Ni 3 N surfaces were converted into amorphous, nano-porous nickel oxide/(oxy)hydroxide surfaces. In the Fe-purified electrolyte, a decrease in OER activity was confirmed after the OER test because of the formation of pure NiOOH with low OER activity and electrical conductivity. Conversely, in the unpurified electrolyte, a continuous increase in OER activity was observed over the OER testing, which may have resulted from the Fe incorporation into the self-oxidation-formed NiOOH. Our experimental findings revealed that Fe impurities play an essential role in obtaining notable OER activity using the Ni 3 N precatalyst. Additionally, our Ni 3 N/Ni foam electrode exhibited a low OER overpotential of 262 mV to reach a geometric current density of 10 mA cm geo −2 in a flow cell with unpurified electrolyte.more » « less
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Abstract Motivated by in silico predictions that Co, Rh, and Ir dopants would lead to low overpotentials to improve OER activity of Ni‐based hydroxides, we report here an experimental confirmation on the altered OER activities for a series of metals (Mo, W, Fe, Ru, Co, Rh, Ir) doped into γ‐NiOOH. The in situ electrical conductivity for metal doped γ‐NiOOH correlates well with the trend in enhanced OER activities. Density functional theory (DFT) calculations were used to rationalize the in situ conductivity of the key intermediate states of metal doped γ‐NiOOH during OER. The simultaneous increase of OER activity with intermediate conductivity was later rationalized by their intrinsic connections to the double exchange (DE) interaction between adjacent metal ions with various
d orbital occupancies, serving as an indicator for the key metal‐oxo radical character, and an effective descriptor for the mechanistic evaluation and theoretical guidance in design and screening of efficient OER catalysts. -
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Abstract Motivated by in silico predictions that Co, Rh, and Ir dopants would lead to low overpotentials to improve OER activity of Ni‐based hydroxides, we report here an experimental confirmation on the altered OER activities for a series of metals (Mo, W, Fe, Ru, Co, Rh, Ir) doped into γ‐NiOOH. The in situ electrical conductivity for metal doped γ‐NiOOH correlates well with the trend in enhanced OER activities. Density functional theory (DFT) calculations were used to rationalize the in situ conductivity of the key intermediate states of metal doped γ‐NiOOH during OER. The simultaneous increase of OER activity with intermediate conductivity was later rationalized by their intrinsic connections to the double exchange (DE) interaction between adjacent metal ions with various
d orbital occupancies, serving as an indicator for the key metal‐oxo radical character, and an effective descriptor for the mechanistic evaluation and theoretical guidance in design and screening of efficient OER catalysts. -
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