Synergistic CNT‐Integrated Ni‐Phthalocyanine/g‐C 3 N 4 Heterojunctional Photocatalysts With Single Ni–N 4 (II) Sites for Efficient Ammonia Synthesis

ABSTRACT The photochemical reduction of nitrogen offers an environmentally friendly approach for ammonia synthesis, providing an alternative to the energy‐intensive and emission‐heavy Haber–Bosch process. Despite its promise, the process is impeded by slow nitrogen activation and excessive hydrogen evolution. To overcome these limitations, we present a tandem nickel phthalocyanine (NiPc)/CNT‐P&Cu‐BCN photocatalyst, engineered with an organic–organic heterojunction for enhanced nitrogen conversion. This system integrates boron‐doped (B), nitrogen‐deficient (N) carbon nitride (CN), modified via Cu–Cu coordination and phosphorus doping through sodium borohydride‐assisted thermal treatment, with hydrogen‐bonded, ultrathin NiPc nanosheets. This novel design yields a record ammonia production rate of 915.4 μmol g −1 h −1 under visible light, a remarkable 16‐fold increase compared to traditional BCN materials. The improvement is attributed to precise bandgap engineering; boron doping and nitrogen vacancies adjust the electronic structure, while the synergistic effects of Cu, P, and CNT enhance charge transfer dynamics. The ultrathin NiPc framework introduces atomically dispersed active sites, whereas a Z‐scheme‐driven charge separation mechanism facilitates efficient electron movement. This work, by integrating defect engineering, heterojunction design, and single‐atom catalysis, contributes to the advancement of photocatalytic nitrogen fixation, offering a scalable pathway for sustainable ammonia production. The results underscore the importance of multi‐component synergy in overcoming kinetic barriers, opening new avenues for energy‐efficient alternatives to conventional synthesis methods.