Benchmarking of Oxygen Adsorption using TPD Spectroscopy for Accurate DFT Prediction of ORR on Anatase Titanium Dioxide (101)
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 O2 adsorption, as few papers in the literature have systematically verified the accuracy of the calculations. Here, we have overcome this issue by comparing calculated O2 adsorption energy (Eads) to simulated Eads distribution from experimental temperature-programmed desorption (TPD) spectrum. The distribution obtained based on equilibrium thermodynamic arguments is in good agreement with the calculated Eads from modelling O2 adsorption on anatase-TiO2(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 O2 thermodynamically as stable as that in the gas phase. In contrast, the calculated Eads for Pt(111) exhibit a significant overestimation of the O2 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.
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