Correction Cite This: ACS Catal. 2018, 8, 6070−6070
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Correction to “A Density Functional + U Assessment of Oxygen Evolution Reaction Mechanisms on β‑NiOOH” Alexander J. Tkalych, Houlong L. Zhuang, and Emily A. Carter* ACS Catal. 2017, 7 (8), 5329−5339. DOI: 10.1021/acscatal.7b00999 1. CORRECTION TO THE SURFACE ENERGY EQUATION The surface area normalization (2A term) was inadvertently neglected in the evaluation of the solvated surface slab energies. The equation appearing in the results section (p. 5333):
original paper1 remains valid, and the primary conclusions are unaffected.
3. ADDITIONAL ACKNOWLEDGMENT We would like to thank Dr. Mark P. Martirez for the critical analysis of the data within this paper that resulted in this correction.
E interface = Esolvation − Evacuum + Esurface
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in which Esurface is the area-normalized surface energy in J/m2, while (Esolvation − Evacuum) was mistakenly evaluated as the solvation energy in eV. Therefore, the equation should be corrected as E interface =
REFERENCES
(1) Tkalych, A. J.; Zhuang, H. L.; Carter, E. A. A Density Functional + U Assessment of Oxygen Evolution Reaction Mechanisms on β -NiOOH. ACS Catal. 2017, 7 (8), 5329−5339. (2) Martirez, J. M. P.; Carter, E. A. Effects of the Aqueous Environment on the Stability and Chemistry of β-NiOOH Surfaces. 2018, submitted for publication (relevant data available upon request).
1 (Esolvation − Evacuum) + Esurface 2A
where (Esolvation − Evacuum) is in J and 2A is in m2. This error consequently renders the data in Table 1 concerning surface energies in water (column 3) incorrect.
2. RETRACTION OF TABLE 1 In ref 1, to obtain surfaces that expose either Ni or OH groups, surface slab models with stoichiometries different from that of the bulk were considered in the original work. This leads to either over-reduced or overoxidized surfaces with energies that significantly deviate from the energies of stoichiometric slabs. Thus, to compare directly surfaces with the same oxidation states, structures that are nonstoichiometric should have not been included in Table 1 (page 5334). The surface energies of the nonstoichiometric surfaces also were evaluated improperly: the chemical potentials of the elements that are either deficient or in excess were not correctly referenced to secondary chemical reservoirs. This makes all data concerning the surface energies of nonstoichiometric surfaces in vacuum (column 2) incorrect, which includes all surfaces except for OH(010) and OH(001). Further, an instability in the predicted bulk structure rendered the surface energy of OH(001) to be too low. Symmetry breaking accessible to the slab used to model this surface allowed for further ionic relaxation. To correct Table 1 (page 5334) in its entirety is too significant an undertaking for a correction; the authors therefore simply retract the entirety of Table 1. A comprehensive study focusing on the various surfaces, including the effects of solvation and explicit water adsorption on their stability are presented instead in ref 2. We refer readers to Table 3 of ref 2, which contains correct surface energies of different facets both in vacuum and using a water solvation model (columns 5 and 6). Ref 2 also reports the symmetry breaking mentioned above, yielding a lower energy bulk structure than had been found previously. Ref 2 does demonstrate that the (001) surface still has the lowest surface energy in both vacuum and aqueous environment, as concluded in our original paper.1 Therefore, the rest of the © XXXX American Chemical Society
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DOI: 10.1021/acscatal.8b01775 ACS Catal. 2018, 8, 6070−6070
