Two-sites are better than one: revisiting the OER mechanism on CoOOH by DFT with electrode polarization

Abstract

We uncover several competitive mechanisms of water oxidation on the β-CoOOH (10–14) surface by explicitly including electrode polarisation and going beyond the classical 4-step mechanism frequently used to study this reaction at the DFT level.

Revisiting the Active Sites at the MoS2/H2O Interface via Grand-Canonical DFT: The Role of Water Dissociation

“…In our approach, the electrode and adsorbates, as well as the surface charge which tunes the electrochemical potential are described via DFT while the electrolyte and solvent are represented by the solution of the linearized Poisson-Boltzmann (PB) equation. 50,51 Previously, we have successfully applied this approach not only to the characterization of the electrochemical interface, 52,53 but also to the elucidation of reaction mechanisms at electrified interfaces such as the oxygen evolution reaction on CoOOH 54 or on iron doped graphenes 55 and even for the electrochemical promotion of catalysis, 56,57 demonstrating its great versatility.…”

Atomistic modeling of electrocatalysis: Are we there yet?

“…The second equality is valid for metallic (gap-less) systems, for which the grand-canonical energy F(U) can be expanded to second order in terms of the capacitance C of the system. In contrast to CHE, the explicit dependence of the electronic energies on the electrochemical potential capture the potential-dependence of formally chemical steps, (113,64) e.g. the desorption of O2 depicted in Figure 4.…”

“…Hence, while η TD tends to be a relevant quantity for screening catalysts, it is clearly not enough for a detailed understanding of reaction mechanism. 64 The second key issue with η TD is that it is such a crude approximation that it is not even clear what experimental quantity it should be compared or correlated to: Is it the overpotential based on the Tafel relation, that is, when the linear approximation becomes valid? The overpotential as determined experimentally based on a limiting current density, often taken as 10 mA/cm 2 and thus more commonly available than a complete Tafel analysis?…”

“…The second equality is valid for metallic (gap-less) systems, for which the grandcanonical energy F(U) can be expanded to second order in terms of the capacitance C of the system. In contrast to CHE, the explicit dependence of the electronic energies on the electrochemical potential captures the potential-dependence of formally chemical steps, 64,113 for example, the desorption of O 2 depicted in Figure 4. The last 10 years or so have seen several computational approaches that all rely on Equation ( 9) to compute potential-dependent adsorption energies on periodic surfaces.…”

“…Since the linearized PB equation assumes that the countercharge is made of point charges, it neglects, however, all finite size effects, resulting in countercharge distributions that approaches the solute too closely. 143 Compared to the homogeneous background method, where an energy correction is needed that assumes that the slab is metallic, the (linearized) Poisson-Boltzmann equation is also readily compatible with semiconductors 64 (Figure 4) and layered electrocatalysts, 144,145 making this approach universally applicable. Indeed, the advantage of the combination of DFT with the linearized Poission-Boltzmann equation is that it can be applied to any charged system, while producing physically meaningful electronic energies.…”