<p>High-density, asymmetrically coordinated transition metal single atoms (TMSAs) are promising for high-performance electrochemical applications. Here we introduce a ‘metal–organic gel-directed pyrolysis’ strategy that enables gram-scale synthesis of Cu single atoms in N and P co-doped carbon (CuN₃O–P/NPC) at a high mass loading of 30.5 wt%. This approach is generalizable to other TMSAs (Fe, Co, Ni, Zn) with similarly high loading and asymmetric coordination. As an electrocatalyst for the nitrate reduction reaction, CuN₃O–P/NPC achieves an ammonia yield of 50.88 mg h⁻¹ mg_cat.⁻¹ with a Faradaic efficiency of 97.3%, outperforming symmetrically coordinated counterparts. Density functional theory calculations show that the potential-limiting step shifts from *NO → *NOH in symmetric analogues to *NOH → *HNOH over CuN₃O–P/NPC, accompanied by a lower free-energy change and more favourable thermodynamics. This work presents a scalable and generalizable strategy for constructing high-density TMSAs with engineered coordination environments for electrocatalysis and energy applications.</p><p></p>