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.