Electrochemical flow cells for the reduction of nitrogen and water to ammonia typically suffer from sluggish reaction kinetics and unfavorable mass transport phenomena. Due to these drawbacks, ammonia, which is a potential fuel with high hydrogen density, is often produced with poor selectivity and in low yields.

Guihua Yu, Zhaoyu Jin, and colleagues, University of Texas at Austin, USA, have developed a surface-strained TiO₂ nanoreactor to enhance the electrocatalytic nitrogen reduction reaction. The nanotubular structure of the reactor regulates mass transport and offers an enlarged surface area. The team first prepared TiO₂ nanotubes via a two-step anodization process and then converted them to lattice-strained TiO₂ nanotubes via the electrochemical intercalation of lithium ions.

The team found that Ti³⁺ sites, which are stabilized by the lattice strain in the material, provide a more favorable pathway for nitrogen activation and allow for a faster kinetic rate than pristine TiO₂. The nanoreactor delivers a high faradaic efficiency of 26 % and an ammonia yield rate of 16.67 µg h^–1 mg^–1. According to the researchers, the work could contribute to the development of optimized nanoreactors for the electrosynthesis of valuable products.

• A Surface-Strained and Geometry-Tailored Nanoreactor that Promotes Ammonia Electrosynthesis,
  Panpan Li, Zhaoyu Jin, Zhiwei Fang, Guihua Yu,
  Angew. Chem. Int. Ed. 2020.
  https://doi.org/10.1002/anie.202011596