Facet-dependent BiOBr(102) facets and oxygen vacancies on BiOBr/BiOCOOH heterojunction for enhance photocatalytic nitrogen fixation

Photocatalytic nitrogen fixation, converting atmospheric nitrogen into ammonia under ambient conditions, offers a sustainable alternative to the Haber-Bosch process. Herein, the hydrothermal and solvothermal methods to prepare the heterojunction based on BiOCOOH nanosheets and BiOBr nanosheets (BiOCOOH/BiOBr) have been reported. The BiOBr nanosheets epitaxially grow along the nanosheets structure of BiOCOOH. The BiOCOOH/BiOBr heterojunction exhibit photogenerated electron–hole separation properties, which was ascribed from the suitable bandgap values for photocatalytic nitrogen fixation. The NH 3 yield of BiOCOOH/BiOBr heterojunction (63.7 μmol·g −1 ·h −1 ) was about 9 times higher than that of pure BiOCOOH with addition of 0.75 mL of methanol as a sacrifice solvent. Moreover, it is confirmed that the texture coefficient of the (102) BiOBr facet between BiOCOOH and BiOBr is positively correlated with photocatalytic performance, which verifies the growth law of BiOBr on BiOCOOH and explains the formation of the heterojunction from a new perspective. The oxygen vacancies from the (102) BiOBr facet can facilitate the adsorption of nitrogen molecules with a stable adsorption energy of 0.1 eV by density functional theory calculations. This study may offer new perspectives for the design of a series of photocatalytic nitrogen fixation catalysts, particularly in terms of crystal facet control and oxygen vacancy-enhanced nitrogen adsorption.