DFT Insights into High-Temperature H₂ Production at Dual-Atom Active Sites on CeO₂

CeO₂-based catalysts have attracted considerable interest in producing H₂ via high-temperature water-splitting reactions, where hydroxyl decomposition into H₂ was reported as the reaction limiting step. By conducting density-functional theory calculations, it was found that direct H₂ production on CeO₂ via hydroxyl decomposition needs to overcome a ∼ 3.0 eV barrier, which competes heavily with an additional water adsorption and dissociation into more hydroxyls. Inducing dual-atom sites in CeO₂ by substituting one Ce with two Pd (Ni or Rh) can effectively reduce the reaction barrier to 1.5-2.0 eV at high hydrogen coverage and therefore improve the turnover frequency of producing H₂ by 10-12 orders of magnitude compared to CeO₂. The decreased activation energy barrier for H₂ generation over dual-atom sites is linearly correlated with the hydrogen adsorption energy. This work provides atomic-level understanding on rational design of dual-atom sites in metal oxide-based catalysts.