• • The NOF pathway requires only 4 electrons versus a minimum of 6 for NRF, reducing the thermodynamic barrier and potentially enabling higher reaction rates; however, reported nitrate yields remain in the micromolar to millimolar range, with apparent quantum efficiencies (AQE) typically below 1% under visible light, indicating that practical solar-to-chemical conversion efficiency is still far from industrial viability.
• • Oxygen vacancies in catalysts such as Nb2O5−x and Bi24O31Cl10 enhance N2 adsorption and activation, with studies demonstrating nitrate production rates up to 17442–17450 μmol g−1 h−1 in electrocatalytic systems; yet, photocatalysis lags by orders of magnitude, highlighting the need for improved charge separation and surface reaction kinetics.
• • Competing oxygen evolution reaction (OER) consumes photogenerated holes, reducing Faradaic efficiency for nitrate synthesis; cation vacancy engineering in RuO2 (Adv Energy Mater, 2023, 13: 2300615) has been shown to optimize the dialectical relationship between NOR and OER, but long-term stability under operational conditions remains unproven beyond 100 hours.
• • The Haber-Bosch process operates at 400–500 °C and 150–300 atm, consuming approximately 1–2% of global energy and emitting 1.6% of global CO2; NOF operates under ambient conditions, but current nitrate production rates (e.g., 140669 μmol g−1 h−1 in plasma-driven systems) are not directly comparable to photocatalytic systems, necessitating standardized metrics for fair evaluation.