Electrochemical Reduction of Nitrogen to Ammonia Using Zinc Telluride

Electrosynthesis of ammonia (NH3), an important constituent molecule of various commercial fertilizers, is a promising and sustainable alternative strategy compared with the century-old Haber-Bosch process. Herein, zinc telluride (ZnTe) is demonstrated as an efficient electrocatalyst for reducing nitrogen (N-2) under ambient conditions to NH3. In this simple chemical strategy, Zn preferentially binds N-2 over hydrogen (H-2), and Te, by virtue of its superior electronic properties, enhances the electrocatalytic activity of ZnTe. The analysis of the X-ray diffraction data using the Bravais-Friedel-Donnay-Harker (BFDH) theory predicted a crystal geometry with the active electrocatalytic sites predominantly confined to the (111) planes of ZnTe. The preferential binding of nitrogen (N-2; adsorption energy = -0.043 eV) over hydrogen (H-2, adsorption energy = -0.028 eV) to Zn on the (111) plane of ZnTe is further confirmed by density functional theory. The ZnTe catalyst is observed to be stable in the acidic medium and delivers a very high yield of NH3 (19.85 mu g/h(-1) mg(cat)(-1)) and a Faradaic efficiency of 6.24% at -0.6 V (versus RHE). Additional verification experiments do not reveal the formation of side products (such as NH2-NH2) during N-2 reduction by ZnTe. Further, density functional theory calculations strongly predict that the electrocatalytic reduction of N-2 to NH3 by ZnTe preferentially occurs via the alternate pathway.