Fig. 5. (a) NH₃ synthesis with N₂ as the feed gas and (b) CO generation with CO₂ as the feed gas at various potentials for BiFeO₃/BiVO₄ hybrids; (c) LSV curves of BiFeO₃/BiVO₄ hybrids in Ar, N₂, CO₂ and N₂ + CO₂ saturated electrolyte; (d) the urea yield rate and faradaic efficiencies and (e) the corresponding product distribution of H₂ (purple color), CO (cyan-blue color), NH₃ (red color) and urea (blue color) for urea production with N₂ and CO₂ as the feed gas at various potentials for BiFeO₃/BiVO₄ hybrids; (f) ¹H NMR spectra of electrolyte saturated with ¹⁵N₂ + CO₂/¹⁴N₂ + CO₂ after 2 h of electrolysis and standard ¹⁵NH₂CO¹⁵NH₂/¹⁴NH₂CO¹⁴NH₂ solution; (g) ¹H NMR spectra of standard ¹⁵NH₂CO¹⁵NH₂ solution at concentrations of 0.2–0.5 μg mL⁻¹; (h) integral area (¹⁵NH₂CO¹⁵NH₂/C₄H₄O₄)–concentration linear relation calibrated using standard ¹⁵NH₂CO¹⁵NH₂ solution; (i) the urea yield of BiFeO₃/BiVO₄ hybrids after 2 h of electrolysis determined using the UV-Vis spectrum and ¹H NMR spectra.