Nitrate reduction to ammonium: from CuO defect engineering to waste NO _x -to-NH ₃ economic feasibility

Critical to the feasibility of electrochemical reduction of waste NO _x (NO _x RR), as a sustainable pathway and to close the NO _x cycle for the emerging NH ₃ economy, is the requirement of inexpensive, scalable and selective catalysts that can generate NH ₄ ⁺ with high yield, as indicated by our economic modelling.