Designing efficient doped NiOOH catalysts for water splitting with first principles calculations

Abstract

Photoelectrochemical cells aim at producing clean fuels with solar energy. However, the major limitation of this technology is the efficiency of the oxygen evolution reaction (OER) occurring at the anode electrode. One of the best catalysts for this reaction is nickel oxyhydroxide (NiOOH) when doped with iron. In this work, we use Density Functional Theory (DFT)+U calculations to systematically scan various metallic dopants for NiOOH. We predict that doping with middle and late transition metals significantly lowers the overpotential. Furthermore, we demonstrate that overpotential value is correlated to the adsorption energies of some specific reaction intermediates and to the chemical nature of the active center. Among the metallic dopants that we considered, late transition metal oxides exhibit great promise for improving reaction efficiency. Our results agree with trends observed in available experiments.

Understanding the Oxygen Evolution Reaction on a Two‐Dimensional NiO2 Catalyst

“…As a consequence, the reaction is not the result of a unique atomic active center. In contrast, as OER happens at NiOOH edges, we were able to clearly distinguish local variations of the oxidation state on some specific Ni atoms …”

“…In order to save a significant computational time, we reduced the k‐mesh to 3×3×1 for the frequency calculations. All those technical parameters allow to reach an accuracy of 0.05 eV regarding the reaction energies, in agreement with usual convergence criteria applied in computational catalysis . Oxidation states were determined on the basis of the atomic magnetization, assuming an octahedral splitting of the d orbitals according to the crystal field theory.…”

“…We performed this work with VASP 5.3 software, using spin polarized calculations in the density functional theory (DFT) framework. We applied the Perdew‐Burke‐Ernzerhof (PBE) exchange‐correlation (XC) functional with a (U−J) parameter of 6 eV for Ni atoms in agreement with previous related studies . We considered the Hubbard correction according to the Dudarev et al.…”

“…Each reaction step, i, is affected by a specific reaction energy, ΔG i . We define the overpotential η in Equation (2), as the difference between the highest reaction energy, max(ΔG i ), and the standard potential of reaction (1), E° H2O (+1.14 V according to DFT, as considered here; vs. +1.23 V for experiment) …”

“…We applied the Perdew-Burke-Ernzerhof (PBE) exchange-correlation (XC) functional [32] with a (UÀJ) parameter of 6 eV for Ni atoms in agreement with previous related studies. [33][34][35] We considered the Hubbard correction according to the Dudarev et al formalism. [36] To model the electron-ion interaction we used projected augmented waves (PAW) pseudopotentials [37] with an energy cutoff of 600 eV.…”