An Experimental Benchmark for the Barrier Height of an On-Surface Reaction: Hydrogen Oxidation on Pt(332)

Developing predictive theories for the rates of reactions between surface-bound molecules is a central challenge to understanding many important phenomena including: heterogeneous catalysis, electrocatalysis, nanofabrication, and corrosion. To meet this challenge, chemically accurate benchmarks to test theoretically derived reaction rates and barrier heights are essential, but few exist. Here, we determine from experiment an accurate zero-point-energy corrected barrier height, 0.76 ± 0.03, for the reaction O* + H* → OH* occurring at atomic Pt B-type step sites, the rate limiting step of hydrogen oxidation on Pt. This experimental benchmark agrees with density functional theory (DFT) predictions made at the level of the generalized gradient approximation (GGA) for five different functionals, exhibiting a mean absolute error (MAE) of 25 meV. This is far better agreement than commonly expected for this level of theory. We speculate that this level of agreement may be a common feature for reactions that involve only species adsorbed on surfaces.