Bi/BSO Heterojunctions via Vacancy Engineering for Efficient Photocatalytic Nitrogen Fixation

Abstract Photocatalytic nitrogen reduction represents a viable technology for green ammonia synthesis under mild conditions. However, the performance of the photocatalysts is typically limited by high charge carrier recombination and low adsorption and activation of nitrogen molecules. Herein, Bi/Bi 2 Sn 2 O 7 (Bi/BSO) heterojunction nanocomposites are prepared via a one‐step hydrothermal method, where NaOH etching of oxygen vacancies in the Bi─O bonds of Bi 2 Sn 2 O 7 (BSO) is exploited for the in situ formation of metallic Bi and hence Schottky junctions with the semiconducting BSO. This leads to a high separation rate of photogenerated charge carriers. Consequently, compared to the pure‐phase BSO, the Bi/BSO heterostructures exhibit markedly enhanced ammonia production, reaching an optimum rate of 284.5 µmol g −1 h −1 , where the rectifying contact between the semiconducting BSO and metallic Bi facilitates directional BSO to Bi electron transfer, leading to enrichment of photogenerated electrons at the active sites of metallic Bi. First‐principles calculations confirm the alteration of active sites and the guided electron flow by the Schottky junctions and surface oxygen vacancies. Results from this study offer an effective paradigm of structural engineering in manipulating the photocatalytic activity of bismuth‐based pyrochlore materials toward nitrogen fixation to ammonia.