fig4

Figure 4. (A) LSV curves of PCN, PCN-Cu-SAC₁, PCN-Cu-SAC₂, PCN-Cu-DAC, and PCN-Cu-NCs in a mixed solution of 1 M KOH and 1 M KNO₃; (B) FE of the PCN, PCN-Cu-SAC₁, PCN-Cu-SAC₂, PCN-Cu-DAC, and PCN-Cu-NCs at different potentials for NRA in 1 M KNO₃ and 1 M KOH mixed solution reproduced with permission from Ref.^[82] copyrights 2025 Wiley-VCH GmbH; (C) NH₃ yield rates at different applied potentials for Cl-Fe-NC SAC, Fe-NC SAC, and NC in a 1 M KOH electrolyte containing 0.1 M KNO₃ from axial chlorine reproduced with permission from Ref.^[83] copyrights 2025 ACS; (D) NH₃ yield rates of N₂S₁Cu-RuN₃/SNC, RuSA/SNC, and CuSA/SNC reproduced with permission from Ref.^[87] copyrights 2025 ACS. LSV: Linear sweep voltammetry; PCN: polymeric carbon nitride; SAC: single-atom catalyst; DAC: dual-atom catalyst; NCs: nitrogen-doped carbons; FE: Faradaic efficiency; NRA: nitrate reduction to ammonia; SNC: S, N co-doped carbon; RHE: reversible hydrogen electrode.