Hydrogen Spillover to Oxygen Vacancy of TiO_{2- x}H_y/Fe: Breaking the Scaling Relationship of Ammonia Synthesis

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, that is, 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 that is counterintuitively founded upon a strong-strong N-bonding pair unveiled in a bifunctional nanoscale catalyst TiO_2-xH_y/Fe (where 0.02 ≤ x ≤ 0.03 and 0 < y < 0.03), in which hydrogen spillover (H) from Fe to cascade oxygen vacancies (O_V-O_V) results in the trapped form of O_V-H on the TiO_2-xH_y component. The Fe component thus enables facile activation of N₂, while the OV-H in TiO_2-xH_y hydrogenates the N or NH_z to NH₃ easily.