In-Situ Construction of Atomic-Level Fe–O Bond Bridges within Fe₂N/g-C₃N₄ Heterojunction for Efficient Visible-Light-Driven Photocatalytic H₂ Production

The limited active sites and faster photogenerated electron-hole pair recombination rate of g-C₃N₄ restrict its application in photocatalytic H₂ production. Constructing heterojunctions has been shown to improve the spatial (directional) separation of photogenerated electrons and holes. However, due to interface mismatch in traditional heterojunction structures and a lack of precise electron transport channels, the photocatalytic efficiency is limited. Here, we developed a two-step calcination approach to create an Fe₂N/g-C₃N₄ heterojunction linked by Fe-O bonds (named as Fe-OCN). The newly formed Fe-O bonds within the heterojunction can act as atomic-level interface electron transfer channels, directly transferring the photogenerated electrons of g-C₃N₄ to the reactive center Fe₂N, significantly improving the charge transfer rate and utilization, thus promoting visible-light-driven photocatalytic H₂ production. The optimal Fe-OCN achieved a H₂ production rate of 5986.29 μmol g^-1 h^-1 under visible light, 13.44 times higher than that of the OCN due to efficient charge separation and transfer capabilities. This work provides a constructive reference for the design and synthesis of organic-inorganic heterojunction with chemically bonded interfaces, establishing quick electron transfer channels, and achieving targeted electron transfer.