Molecular Wiring of Electrocatalytic Nitrate reduction to Ammonia and Water Oxidation by Iron-Coordinated Macroporous Conductive Networks

Abstract

Developing stable electrocatalysts with accessible isolated sites is desirable but highly challenging due to metal agglomeration and low surface stability of host materials. Here we report a general approach for synthesis of single-site Fe electrocatalysts by integrating a solvated Fe complex in conductive macroporous organic networks through redox-active coordination linkages. Electrochemical activation of the electrode exposes high-density coordinately unsaturated Fe sites for efficient adsorption and conversion of reaction substrates such as NO3- and H2O. Using the electrode with isolated active Fe sites, electrocatalytic NO3- reduction and H2O oxidation can be coupled in a single cell to produce NH3 and O2 at Faradaic efficiencies of 97% and 100%, respectively. The electrode exhibits excellent robustness in electrocatalysis for 200 hours with small decrease in catalytic efficiencies. Both the maximized Fe-site efficiency and the microscopic localization effect of the conductive organic matrix contribute to the high catalytic performances, which provides new understandings in tuning the efficiencies of metal catalysts for high-performance electrocatalytic cells.

Keywords: Molecular electrocatalysts; conductive polymer; nitrate reduction to ammonia; single iron catalysts; water oxidation.