Gas‐Phase Errors Affect DFT‐Based Electrocatalysis Models of Oxygen Reduction to Hydrogen Peroxide

Abstract

Electrochemical production of H2O2 is more benign and affordable than the conventional route, yet its adoption requires the discovery of robust, cost‐effective catalysts. DFT‐based models lead to conspicuous breakthroughs but had some known limitations, for instance the poor description of molecules with certain chemical bonds. Here, the errors in H2O2 and O2 displayed by various GGAs, meta‐GGAs and hybrids were assessed and semi empirically corrected. The errors in O2 with respect to experiments were in the range of −0.95 to −0.22 eV, whereas those in H2O2 spanned from −0.53 to −0.04 eV. Thus, single and double O−O bonds were poorly described in general, and the errors were nearly twice as negative for double bonds. Furthermore, these errors introduced large deviations in the predictions of free energies for O2 reduction to H2O2, and the equilibrium potentials and optimal adsorption energies of *OOH could either be sizably overestimated or underestimated.

Automated versus Chemically Intuitive Deconvolution of Density Functional Theory (DFT)-Based Gas-Phase Errors in Nitrogen Compounds

“…In addition, gas-phase corrections have also been shown to improve the prediction of equilibrium and onset potentials for the electroreduction of CO 2 to CO, and brought DFT-calculated adsorption energies of CO on several metals closer to experimental values . Finally, the importance of gas-phase corrections has also been illustrated for free-energy diagrams and volcano plots for O 2 reduction and evolution , and H 2 O 2 production …”

“…The DFT calculations were performed using the Vienna ab initio simulation package (VASP), the Perdew–Burke–Ernzerhof (PBE) exchange-correlation functional, and the projector augmented-wave (PAW) method . The plane-wave cutoff for all the calculations was 450 eV, shown previously ,, and verified in Figure S2 in the Supporting Information for N 2 O formation to provide converged reaction energies. Gaussian smearing with k B T = 10 –3 eV was used and all energies were extrapolated to 0 K. During the structural optimization of the molecules, carried out using the conjugate gradient algorithm, all atoms were allowed to relax in all directions until the maximal atomic forces were equal to or smaller than 0.01 eV/Å.…”

“…Likewise, if the molecule does not contain oxygen (e.g., NH 3 ), z = 0 in eq . Following previous works, ,,, the total error in the DFT description of a generic nitrogen compound (ε H x N y O z T ) is defined as the difference between the DFT-calculated and the experimental energies of formation, see eq . In this case, we will make the analysis in terms of Gibbs energies of formation (Δ f G H x N y O z DFT and Δ f G H x N y O z exp ).…”

“…50 Finally, the importance of gasphase corrections has also been illustrated for free-energy diagrams and volcano plots for O 2 reduction and evolution 39,51 and H 2 O 2 production. 40 Furthermore, if a given compound X participates in a catalytic reaction but no experimental data are available for it, one can decompose it in its bonds and/or groups of atoms and anticipate the errors present in its DFT-calculated free energy of formation. However, it is recommendable to make an ensemble of predictions based on different matrix representations and establish a correction range rather than a specific correction.…”

Linking Experimental and Ab-initio Thermochemistry of Adsorbates with a Generalized Thermochemical Hierarchy

“…A higher amount of error cancellation can be expected when assuming physisorbed species, since the typical DFT functionals that perform well for adsorbates are often less accurate at predicting gas-phase energies. 9,[38][39][40] Following the formalism, the adsorption site is treated as a single Pt atom that can have either single, double, or triple bonds that can be saturated with H, too. The reaction is then balanced with the required amount of H * 2 .…”