Potassium Promoted Ferrocene/Graphene for Ammonia Synthesis

Innovation of catalysts for mild condition ammonia synthesis promotes the carbon neutrality. Herein we report that ferrocene supported on reduced graphene oxide (rGO) and promoted by alkali metal K is active catalyzing NH3 synthesis from N2/H2 mixture. It exhibits a NH3 formation rate of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0.1\,\,{\rm{\mu mo}}{{\rm{l}}_{{\rm{N}}{{\rm{H}}_3}}} \cdot g_c<^>{ - 1} \cdot {{\rm{h}}<^>{ - 1}}$$\end{document} at 190 degrees C and increases by one order of magnitude to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2.1\,\,{\rm{\mu mo}}{{\rm{l}}_{{\rm{N}}{{\rm{H}}_3}}} \cdot g_c<^>{ - 1} \cdot {{\rm{h}}<^>{ - 1}}$$\end{document} at 230 degrees C and under 0.1 MPa. By contrast, both rGO promoted by K and ferrocene supported on rGO without K promotion are almost inactive under the same conditions. Density functional theory calculations validate the essential role of K promoter for facilitating the adsorption of N2 at the coordination unsaturated iron sites in the cyclopentadienylidene form. This finding could guide further development of metal complex catalysts for mild condition ammonia synthesis.