Highly Active and Selective Electroreduction of N2 by the Catalysis of Ga Single Atoms Stabilized on Amorphous TiO2 Nanofibers

The electroreduction of N-2 under ambient conditions has emerged as one of the most promising technologies in chemistry, since it is a greener way to make NH 3 than the traditional Haber-Bosch process. However, it is greatly challenged with a low NH3 yield and faradaic efficiency (FE) because of the lack of highly active and selective catalysts. Inherently, transition (d-block) metals suffer from inferior selectivity due to fierce competition from H-2 evolution, while post-transition (p-block) metals exhibit poor activity due to insufficient pi back-donation behavior. Considering their distinct yet complementary electronic structures, here we propose a strategy to tackle the activity and selectivity challenge through the atomic dispersion of p-block metal on an all-amorphous transition-metal matrix. To address the activity issue, lotus-root-like amorphous TiO2 nanofibers are synthesized which, different from vacancy-engineered TiO2 nanocrystals reported previously, possess abundant intrinsic oxygen vacancies (V-O) together with under-coordinated dangling bonds in nature, resulting in significantly enhanced N-2 activation and electron transport capacity. To address the selectivity issue, well-isolated single atoms (SAs) of Ga are successfully synthesized through the confinement effect of V-O, resulting in Ga-V-O reactive sites with the maximum availability. It is revealed by density functional theory calculations that Ga SAs are favorable for the selective adsorption of N-2 at the catalyst surface, while V-O can facilitate N-2 activation and reduction subsequently. Benefiting from this coupled activity/selectivity design, high NH3 yield (24.47 mu g h(-1) mg(-1)) and FE (48.64%) are achieved at an extremely low overpotential of -0.1 V vs RHE.

Automated summary

The electroreduction of N-2 under ambient conditions is a promising technology to produce NH3 in a more environmentally friendly way. However, the low yield and efficiency of NH3 production have been challenging due to the lack of highly active and selective catalysts. This study proposes a strategy to address the activity and selectivity challenge by dispersing p-block metal atoms on an all-amorphous transition-metal matrix.