In-Situ Construction\nof Atomic-Level Fe–O Bond\nBridges within Fe<sub>2</sub>N/g‑C<sub>3</sub>N<sub>4</sub> Heterojunction for Efficient Visible-Light-Driven Photocatalytic\nH<sub>2</sub> Production

The limited active sites and faster photogenerated electron–hole\npair recombination rate of g-C<sub>3</sub>N<sub>4</sub> restrict its\napplication in photocatalytic H<sub>2</sub> production. Constructing\nheterojunctions has been shown to improve the spatial (directional)\nseparation of photogenerated electrons and holes. However, due to\ninterface mismatch in traditional heterojunction structures and a\nlack of precise electron transport channels, the photocatalytic efficiency\nis limited. Here, we developed a two-step calcination approach to\ncreate an Fe<sub>2</sub>N/g-C<sub>3</sub>N<sub>4</sub> heterojunction\nlinked by Fe–O bonds (named as Fe-OCN). The newly formed Fe–O\nbonds within the heterojunction can act as atomic-level interface\nelectron transfer channels, directly transferring the photogenerated\nelectrons of g-C<sub>3</sub>N<sub>4</sub> to the reactive center Fe<sub>2</sub>N, significantly improving the charge transfer rate and utilization,\nthus promoting visible-light-driven photocatalytic H<sub>2</sub> production.\nThe optimal Fe-OCN achieved a H<sub>2</sub> production rate of 5986.29\nμmol g<sup>–1</sup> h<sup>–1</sup> under visible\nlight, 13.44 times higher than that of the OCN due to efficient charge\nseparation and transfer capabilities. This work provides a constructive\nreference for the design and synthesis of organic–inorganic\nheterojunction with chemically bonded interfaces, establishing quick\nelectron transfer channels, and achieving targeted electron transfer.