Spatially Engineered Dual S‐Scheme Heterojunctions with Significantly Enhanced Space Charge Separation for Boosting Artificial Photosynthetic Nitrogen Fixation

ABSTRACT Artificial photosynthetic nitrogen fixation presents a promising alternative to the conventional Haber–Bosch process. However, the precise construction of heterojunction photocatalysts with efficient spatial charge separation remains a formidable challenge. Herein, a dual S‐scheme heterojunction system, Bi 2 O 2 CO 3 /g‐C 3 N 4 /SrTiO 3 (denoted as BOC/CN/STO), is designed and successfully synthesized for solar‐driven nitrogen fixation. Benefiting from the synergistic effect of the dual S‐scheme electron migration pathway and a strong internal electric field, the separation and migration of photogenerated carriers in this system are greatly enhanced. As a result, the optimized BOC/CN/STO photocatalyst exhibits an impressive ammonia production rate of 2173.11 µmol g −1 h −1 , which are 11.98, 14.05, and 13.37 times higher than those of pristine BOC, CN, and STO, respectively. Femtosecond transient absorption (fs‐TA) spectroscopy, Kelvin probe force microscopy (KPFM), and photoelectrochemical tests consistently confirm prolonged electron lifetimes and suppressed recombination of photogenerated electron–hole pairs, both of which are critical for the enhanced nitrogen fixation performance. Experimental and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses further elucidate an alternating hydrogenation pathway for nitrogen fixation over the BOC/CN/STO heterojunction. This work paves the way for the rational design and controllable synthesis of efficient dual S‐scheme artificial photosynthetic systems toward sustainable ammonia synthesis.