Toward a sustainable energy cycle, H2 economy has been considered as one of the most promising solutions to overcome drawbacks of the current fossil fuel economy since it does not emit any pollutants or greenhouse gases during conversion processes . However, 96 % of the current H2 production relies on thermochemical conversions of carbon-based fuels via pyrolysis, gasification and steam reforming of natural gas, requiring clean alternative methods . Water electrolysis has been investigated to produce green H2, which consists of H2 evolution reaction (HER) at the cathode and O2 evolution reaction (OER) at the anode . While the cathodic reaction is considerably facile and various types of catalysts could be employed, the anodic reaction suffers from large overpotentials and harsh operating conditions, requiring noble metal-based oxide catalysts such as Ir and Ru oxides . As an alternative anodic reaction, electrochemical ammonia (NH3) oxidation reaction (AOR) has several advantages over OER . The operating potential (< 1 VRHE) of AOR is much lower than that of OER (> 1.5 VRHE), thus catalyst materials are not limited to oxides as in OER. In addition, the equilibrium potential for N2/NH3 is 0.06 VRHE, indicating that, when coupled with HER, theoretically 95 % less electrical energy is required compared to OER of which the equilibrium potential is 1.23 VRHE .