Modulation of built-in electric field and d-band center via morphology engineering of Bi-Bi₃TaO₇ Schottky heterojunctions toward efficient photocatalytic nitrogen fixation

Hydrothermal synthesis of Bi-Bi 3 TaO 7 heterostructures with mannitol • Morphological evolution from nanoflakes to nanoparticles • Enhanced visible absorption and charge separation by modulation of d-band center • Photocatalytic performance of nitrogen fixation up to 10 times that of pristine Bi 3 TaO 7 Morphology control can effectively regulate the interfacial electric field and electronic structure of photocatalytic materials, making it an important strategy for achieving efficient nitrogen fixation. In this study, a facile one-step hydrothermal method is used, with mannitol as both a reducing agent and morphology regulator, to in situ deposit metallic bismuth nanoparticles onto the surface of Bi₃TaO₇ (BTO), forming Bi-Bi₃TaO₇ (Bi-BTO) Schottky heterojunctions. The Bi-BTO samples consist of nanoparticles as compared to nanosheets for pure BTO, which not only increases the specific surface area and accessibility of catalytic active sites but also effectively regulates the interfacial contact of the Schottky heterojunction. This strengthens the built-in electric field and shifts the d-band center closer to the Fermi level. The optimized electronic structure enhances orbital coupling between the catalyst and nitrogen molecules, promoting nitrogen adsorption and activation and lowering the energy barrier for the formation of the rate-determining *NNH intermediate. Thanks to the synergistic effect of morphology engineering on the built-in electric field and d-band center, the optimal sample Bi-BTO-2 shows an excellent photocatalytic nitrogen fixation performance even without a hole scavenger, achieving an ammonia generation rate of 195 μmol·g −1 ·h −1 , 10 times that of pure BTO, with ammonia selectivity approaching 100%. This study highlights the key role of morphology engineering in regulating the interfacial properties and electronic structure of Schottky heterojunctions, providing a practical modification strategy for the design and engineering of high-performance photocatalysts for nitrogen fixation. Download: Download high-res image (176KB) Download: Download full-size image