Benchmarking of Oxygen Adsorption using TPD Spectroscopy for Accurate DFT Prediction of ORR on Anatase Titanium Dioxide (101)

TL;DR

This study benchmarks the accuracy of DFT calculations of O$_2$ adsorption energies on anatase TiO$_2$(101) by comparing them with experimental TPD spectra, revealing the importance of appropriate van der Waals functionals for reliable predictions of ORR initiation.

Contribution

It introduces a systematic approach using TPD spectroscopy to validate and improve the accuracy of DFT predictions for O$_2$ adsorption on catalytic surfaces.

Findings

vdW-DF3-opt2 provides accurate O$_2$ adsorption energies on TiO$_2$(101)

O$_2$ initiates ORR as a thermodynamically stable physisorbed species

Overestimation of O$_2$ adsorption on Pt(111) due to excessive vdW correction

Abstract

Despite the wide use of first-principles calculations to elucidate catalytic reaction mechanisms, the reliability of the theory remains unknown for reactions that initiate with O$_2$ adsorption, as few papers in the literature have systematically verified the accuracy of the calculations. Here, we have overcome this issue by comparing calculated O$_2$ adsorption energy ($E_{\text{ads}}$) to simulated $E_{\text{ads}}$ distribution from experimental temperature-programmed desorption (TPD) spectrum. The distribution obtained based on equilibrium thermodynamic arguments is in good agreement with the calculated $E_{\text{ads}}$ from modelling O$_2$ adsorption on anatase-TiO$_2$(101) using the generalized gradient approximation and van der Waals density functionals (vdW-DFs) with Hubbard correction, which is particularly the case when vdW-DF3-opt2 is used. On this basis, we concluded that the oxygen reduction reaction (ORR) initiates from a physisorbed O$_2$ thermodynamically as stable as that in the gas phase. In contrast, the calculated $E_{\text{ads}}$ for Pt(111) exhibit a significant overestimation of the O$_2$ adsorption due to excessive vdW correction. Therefore, a systematic investigation based on TPD spectroscopy can be used to diagnose the reliability of theoretical predictions of ORR and is expected to lead to improvements in exchange-correlation functionals for catalysts.