High-efficiency electrocatalytic nitrite-to-ammonia conversion on molybdenum doped cobalt oxide nanoarray at ambient conditions.

Abstract

Electrochemical conversion of nitrite (NO₂^-) contaminant to green ammonia (NH₃) is a promising approach to achieve the nitrogen cycle. The slow kinetics of the complex multi-reaction process remains a serious issue, and there is still a need to design highly effective and selective catalysts. Herein, we report that molybdenum doped cobalt oxide nanoarray on titanium mesh (Mo-Co₃O₄/TM) acts as a catalyst to facilitate electroreduction of NO₂^- to NH₃. Such a catalyst delivers an extremely high Faradaic efficiency of 96.9 % and a corresponding NH₃ yield of 651.5 μmol h^-1 cm^-2 at -0.5 V with strong stability. Density functional theory calculations reveal that the introduction of Mo can induce the redistribution of electrons around Co atoms and further strengthen the adsorption of NO₂^-, which is the key to facilitating the catalytic performance. Furthermore, the assembled battery based on Mo-Co₃O₄/TM suggests its practical application value.