TY - JOUR
T1 - Effects of the Aqueous Environment on the Stability and Chemistry of β-NiOOH Surfaces
AU - Martirez, John Mark P.
AU - Carter, Emily Ann
N1 - Funding Information:
This article is based upon work supported by the Air Force Office of Scientific Research under AFOSR Award No. FA9550-14-1-025. E.A.C. thanks the High Performance Computing Modernization Program (HPCMP) of the U.S. Department of Defense and Princeton University’s Terascale Infrastructure for Groundbreaking Research in Engineering and Science (TIGRESS) for providing the computational resources. We would also like to thank Mr. Alexander J. Tkalych, Ms. Nari L. Baughman, Dr. Johannes M. Dieterich, Dr. Shenzhen Xu, and Dr. Sai Gautam Gopalakrishnan for reading and editing the manuscript. The atomic structures are visualized using VESTA.58
Publisher Copyright:
© 2018 American Chemical Society.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/8/14
Y1 - 2018/8/14
N2 - Nickel oxyhydroxide (NiOOH)-based anodes are among the most promising materials for the electrocatalytic production of oxygen from water under alkaline conditions. We explore the stability of the low-index facets of the catalytically active β-NiOOH phase, namely the (0001), {101N} surfaces, and the as yet unexplored {112N} surfaces, via density functional theory with a Hubbard-U like correction on Ni. We find that their relative stabilities depend strongly on the coordination number of the exposed Ni (cnNi) and O (cnNi). In the vacuum, where passivation of the surface dangling bonds is limited, the stability order is as follows: (0001) > {101N} ≥ {112N}, noting that the coordination numbers for each phase are, respectively, cnNi = 6, 5, and 4, and cnO = 3-4, 2-3, and 2-3. In aqueous media, the order of stability is (0001) > {101N} ≈ {112N}, as the cnNi and cnO of the latter two surface types increase due to water coordination and dissociation. Water adsorption is found to be most favorable on the {112N} surfaces, giving rise to fivefold-coordinated Ni (Ni5c) or Ni6c from Ni4c. Our work suggests that a plethora of facets are likely to coexist on β-NiOOH crystallites with water serving to equalize the stabilities of the different surfaces.
AB - Nickel oxyhydroxide (NiOOH)-based anodes are among the most promising materials for the electrocatalytic production of oxygen from water under alkaline conditions. We explore the stability of the low-index facets of the catalytically active β-NiOOH phase, namely the (0001), {101N} surfaces, and the as yet unexplored {112N} surfaces, via density functional theory with a Hubbard-U like correction on Ni. We find that their relative stabilities depend strongly on the coordination number of the exposed Ni (cnNi) and O (cnNi). In the vacuum, where passivation of the surface dangling bonds is limited, the stability order is as follows: (0001) > {101N} ≥ {112N}, noting that the coordination numbers for each phase are, respectively, cnNi = 6, 5, and 4, and cnO = 3-4, 2-3, and 2-3. In aqueous media, the order of stability is (0001) > {101N} ≈ {112N}, as the cnNi and cnO of the latter two surface types increase due to water coordination and dissociation. Water adsorption is found to be most favorable on the {112N} surfaces, giving rise to fivefold-coordinated Ni (Ni5c) or Ni6c from Ni4c. Our work suggests that a plethora of facets are likely to coexist on β-NiOOH crystallites with water serving to equalize the stabilities of the different surfaces.
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U2 - 10.1021/acs.chemmater.8b01866
DO - 10.1021/acs.chemmater.8b01866
M3 - Article
AN - SCOPUS:85049689722
SN - 0897-4756
VL - 30
SP - 5205
EP - 5219
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 15
ER -