Thermal‐Assisted Photosynthesis of Nitric Acid From Air

Abstract Photocatalytic nitrogen oxidation reactions has emerged as promising techniques for air‐based nitrate synthesis, bolstering sustainable nitrogen fixation in industrial chains centered around nitrates. However, significant disparities in orbital energy levels impose constraints on N₂ conversion, highlighting the pivotal role of nitrogen activation, particularly in oxygen‐rich environments. Herein, a novel Ir‐WO₃ catalyst with cation vacancy chains is fabricated and utilized as a highly efficient catalyst for thermal‐assisted nitrogen oxidation under an innovative discontinuous light illumination strategy. Remarkably, an unexpected NO₃⁻ yield of 381.21 µmol g⁻¹ h⁻¹ is achieved, marking a 10.4‐fold increase compared to regular continuous light illumination. This exceptional performance is attributed to the unique structure and discontinuous light illumination, which lowered the energy barrier of the rate‐determining step for forming *NN(OH) intermediates and enhanced the abundance of •OH. Furthermore, a novel •OH assisted nitrogen activation mechanism is proposed based on the identification of crucial N₂O intermediate and operando experiments. This work offers novel insights into free radicals‐based photocatalytic conversion processes and also presents a potential nitrate synthesis pathway for nitrates‐centric industrial nitrogen fixation chains.