(560bw) Probing the Oxygen Evolution Reaction Efficacy of Pure and Doped NiOOH (0001) Using Hybrid Density Functional Theory

The splitting of water into oxygen and hydrogen is a pre-requisite for a clean, hydrogen-based fuel economy. Alternatively, the electrons and protons produced during the process can be used to reduce carbon dioxide. While the hydrogen evolution reaction involves two electrons, no water molecule, and exhibits a standard potential of 0.0 V, the oxygen evolution reaction (OER) involves four electrons, two water molecules, and exhibits a standard potential of -1.23 V, thereby involving a greater level of complexity. Nickel oxyhydroxide (NiOOH) is a promising 2D material candidate to replace expensive, conventional noble metal catalysts. However, so far, understanding of the electrocatalytic activity of the most-abundant, basal (0001) plane of this material has been obtained using standard density functional theory (DFT) calculations with a Hubbard-like correction term (DFT+U) for the d electrons, wherein the results depend on the on-site Coulomb (U) and exchange (J) parameters. For doped systems, this presents an added level of complexity, because of the use of different values of the U and J parameters for various elements, in order to appropriately avoid the self-interaction error for the localized d electrons. In this work, we instead apply hybrid DFT calculations, which include a fraction of exact exchange, to estimate lower bounds for the OER overpotential on both pure and doped versions of NiOOH, for the associative OER mechanism. By contrasting and rationalizing results, including the magnetic moments and the oxidation states of the adsorbed species and active sites, from these two different levels of theory, we are able to provide new insights into the electrocatalytic activity of the NiOOH basal plane.