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

Abstract

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.