Renewable ammonia (NH3) is a critical vector in enabling decarbonization of global agriculture, chemical and energy industry. The renewable power-to-X chemical is commonly referred as Hydrogen 2.0, as it is stable and can be transported over large jurisdictional distances using current infrastructure. Of the various renewable ammonia production routes, the conversion of waste NOx present in environment and industry presents an economic opportunity to generate ammonia through electrochemical nitrate reduction reactions (NOxRR). Our economic modelling revealed that catalyst performance improvement is critical in enabling the feasibility of NOxRR within industrial setting. In this latest paper published in Energy & Environmental Science, we explore the defect engineering of CuO nanomaterials as potential strategy to improve NOxRR catalysis, revealing a direct correlation between oxygen vacancy density with ammonium (NH4+) yield. Our findings on defect engineering to improve NH4+ yield and its economic feasibility display the potential of NOxRR as an alternative pathway to generate green NH3, which can also serve as an energy vector for the emerging hydrogen economy and close the NOx cycle.