Practical Cluster Models for a Layered β-NiOOH Material

Abstract

Due to the high oxygen evolution reaction (OER) activity, stability, and abundance of NiOx materials, they are found to be promising catalysts, competitive with expensive metal oxides such as IrO2 and RuO2. From a theoretical point of view, studies reported in the literature so far are mostly based on density functional theory using periodic slab models for the bulk and surface of β-NiOOH, one of the active NiOx phases. However, cluster models are a valid method to investigate many aspects about structure, charge carrier transport properties, and OER activity of β-NiOOH. Hence, here we present new cluster models for the surface of β-NiOOH, where the oxygen atoms are bonded to Mg effective core potentials (ECPs) mimicking neighboring atom cores. This cluster embedding procedure is superior to saturating the cluster with hydrogen atoms, and to using other atomic ECPs for β-NiOOH. We find that layered materials such as β-NiOOH are more vulnerable to geometrical rupture and therefore a cluster approach requires additional care in choosing the embedding approach. We evaluated the models by using them to calculate the energy required for water adsorption and deprotonation, which are essential ingredients for OER. Specifically, our results agree with previous slab models that the first deprotonation reaction step requires a large amount of energy. In addition, we find that water and hydroxyl groups have high adsorption energy and therefore the first deprotonation step is limiting the reaction efficiency.

Controlling Water Oxidation Catalysis through Interlayer Arrangements and Vacancies toward Producing Clean Hydrogen

“…Previous studies have reported that β-NiOOH is more reactive to OER than β-Ni­(OH) 2 phase. − In our calculations regarding the catalysis of OER, we removed half of the hydrogen atoms to transform the β-Ni­(OH) 2 into β-NiOOH and optimized the heterostructure. By that, we consider that in the work of Jia et al, local phase transformation in the nickel layer has occurred during the electrochemical cycle so that OER proceeds.…”

DFT Study of GaN Clusters Decorated with Rh and Pt Nanoparticles for the Photochemical Reduction of CO2

“…Investigations based on a cluster model approach can be advantageous over periodic boundary condition (PBC) methods because they enable the use of hybrid functionals at a lower computational cost, and, therefore, a highly accurate description of electronic properties. Moreover, cluster approaches are more appropriate for studying charged systems, thanks to the ability to add/subtract a charge carrier without suffering from interactions with similar charge carriers due to periodic boundary conditions. , Due to their reduced size, cluster approaches can be used to investigate complex reaction mechanisms, allowing for the interception of all the involved stationary points, including the more complex transition states. − However, PBC calculations allow for modeling more extended surfaces and provide an accurate description of the structural properties of the surface and molecular adsorbates. The complementarity of the two computational methods can therefore lead to an in-depth understanding of the structure–property relationship …”

“…Moreover, cluster approaches are more appropriate for studying charged systems, thanks to the ability to add/subtract a charge carrier without suffering from interactions with similar charge carriers due to periodic boundary conditions. 28,29 Due to their reduced size, cluster approaches can be used to investigate complex reaction mechanisms, allowing for the interception of all the involved stationary points, including the more complex transition states. 30−32 However, PBC calculations allow for modeling more extended surfaces and provide an accurate description of the structural properties of the surface and molecular adsorbates.…”

Gallium Nitride‐based Materials as Promising Catalysts for CO2 Reduction: A DFT Study on the Effect of CO2 Coverage and the Incorporation of Mg Doping or Substitutional In

“…[34][35][36][37][38][39][40][41][42] Motivated by these promising results, in a preliminary work, [24] we have investigated the photocatalytic activity of the undoped GaN and GaN doped with one single Mg atom, along with the CO 2 reduction to methanol. The DFT investigation was carried out using a cluster model approach, that has some advantages over periodic boundary condition (PBC) calculations such us the utilization of hybrid functionals, [43][44][45] and the investigation of complex reaction mechanism, [46,47] at lower computational cost than periodic boundary condition (PBC) calculations. However, cluster model approaches do not allow for the investigation of extended surfaces and heterojunctions, which can be more conveniently performed by means of PBC calculations.…”