Hydrogen Spillover to Oxygen Vacancy of TiO2–xHy/Fe: Breaking the Scaling Relationship of Ammonia Synthesis

Abstract

Optimizing kinetic barriers of ammonia synthesis to reduce the energy intensity has recently attracted significant research interest. The motivation for the research is to discover means by which activation barriers of N2 dissociation and NHz (z = 1-2, surface intermediates) destabilization can be reduced simultaneously, i.e., breaking the “scaling relationship”. However, by far only a single success has been reported in 2016 based on the discovery of a strong-weak N-bonding pair—transition metals (nitrides)-LiH. Described herein is a second example which is counter-intuitively founded upon a strong-strong N-bonding pair unveiled in a bifunctional nanoscale catalyst TiO2-xHy/Fe (where 0.02 ≤ x ≤ 0.03 and 0 < y < 0.03), in which hydrogen spillover (H) from Fe to cascade oxygen vacancies (OV-OV) results in the trapped form of OV-H on the TiO2-xHy component. The Fe component thus enables facile activation of N2 and H2, while the OV-H in TiO2-xHy hydrogenates the NHz to NH3 easily.