Amorphous Chromium Oxide with Hollow Morphology for Nitrogen Electrochemical Reduction under Ambient Conditions.

ABSTRACT

The electrocatalytic nitrogen reduction reaction (NRR), an alternative method of nitrogen fixation and conversion under ambient conditions, represents a promising strategy for tackling the energy-intensive issue. The design of high-performance electrocatalysts is one of the key issues to realizing the application of NRR, but most of the current catalysts rely on the use of crystalline materials, and shortcomings such as a limited number of catalytic active sites and sluggish reaction kinetics arise. Herein, an amorphous metal oxide catalyst H-CrOx/C-550 with hierarchically porous structure is constructed, which shows superior electrocatalytic performance toward NRR under ambient conditions (yield of 19.10 µg h-1 mgcat-1 and Faradaic efficiency of 1.4% at -0.7 V vs a reversible hydrogen electrode, higher than that of crystalline Cr2O3 and solid counterparts). Notably, the amorphous metal oxide obtained by controlled pyrolysis of metal-organic frameworks (MOFs) possess abundant unsaturated catalytic sites and optimized conductivity due to the controllable degree of metal-oxygen bond reconstruction and the doping of carbon materials derived from organic ligands. This work demonstrates MOF-derived porous amorphous materials as a viable alternative to current electrocatalysts for NH3 synthesis at ambient conditions.