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

Despite the wide use of first-principles calculations to elucidate catalytic reaction mechanisms, their reliability remains unknown for reactions initiated by O2 adsorption, as few studies have systematically verified the accuracy of these calculations. Herein, we overcome this issue by comparing calculated O2 adsorption energy (Eads) with simulated Eads distribution from the experimental temperature-programmed desorption (TPD) spectrum. The distribution obtained using equilibrium thermodynamic arguments shows excellent agreement with calculated Eads values by modeling O2 adsorption on anatase-TiO2(101) using the generalized gradient approximation and van der Waals density functionals (vdW-DFs) with Hubbard corrections, which is particularly the case when vdW-DF3-opt2 is used. Based on this comparison, we conclude that the oxygen reduction reaction (ORR) initiates from physisorbed O2 that is thermodynamically as stable as that in the gas phase. In contrast, the calculated Eads values for Pt(111) significantly overestimate O2 adsorption due to an excessive van der Waals correction. Therefore, systematic investigation using TPD spectroscopy can be employed to assess the reliability of theoretical predictions of the ORR and may contribute to improving exchange–correlation functionals for catalytic systems.