D–Band Contraction of Metal Nitride Nanosheets Enables Highly Efficient and Stable Electrochemical Oxidation of Ammonia

Ammonia is a promising hydrogen carrier as it reduces the cost of long–range transportation of hydrogen. Ammonia electrolysis provides a convenient method to extract hydrogen from ammonia at end users. However, the conventional platinum carbon electrode suffers from fast degradation and electrode fouling at electrode–electrolyte interface during the ammonia electrochemical oxidation(AOR). Here, we report that nitriding electrochemical deposited nickel cobalt layered double hydroxide nanosheets can achieve high electrocatalytic activity for AOR in non–aqueous solution. The AOR onset overpotential of NiCo2N nanosheets is 0.55 V which is about 0.25 V lower than that of the platinum carbon electrode. Ultraviolet–visible and Mass spectroscopy studies reveal NiCo2N nanosheets can suppress the formation of metal amine complex and preferentially oxidize ammonia to N2 with a faradic efficiency of over 90 percent. DFT calculation indicates that the downshift of the metal d–band center on NiCo2N nanosheets surface accelerated the generation of NH+ X cations and desorption of final N2*, boosting ammonia electrochemical oxidation toward N2. Overall, this work introduces a practical strategy for synthesizing an active and stable electrocatalyst for AOR.