Epitaxial Bi₄O₅Br₂ nanosheets on hollow carbon spheres for confined electron pump reactor and enhanced photocatalytic CO₂ hydrogenation reduction

In order to enhance the efficiency of artificial photosynthesis, it is imperative to improve the hysteretic migration and separation efficiency of photogenerated charge carriers. Herein, ultrathin Bi₄O₅Br₂ (BOB) nanosheets are prepared vertically and uniformly on the surface of hollow N-doped carbon spheres (NC) to produce a hollow confined nanoreactor (BOB@NC). The graphite layer and N in NC act as a tandem electron pump for the rapid transfer of photogenerated electrons from BOB to the NC surface via the Bi-C bridging bond between BOB and NC, and the electrons on the NC surface continue to move to the N-induced defect energy levels. This NC electron pump facilitates the transfer of the photogenerated electrons in a directional, rapid, and efficient manner. Meanwhile, the adsorption of CO₂ molecules and hydrogenation of *CO to *CHO at the N site on NC are kinetically spontaneous, thereby significantly reducing the CO₂ reduction reaction energy barrier of BOB. As a result, the efficiency of CO₂ hydrogenation reduction to CO and CH₄ by BOB@NC is 3.31 and 11.15 times higher than that by the BOB monomer, respectively. The hollow confined electron pump reactor reveals a novel strategy for the design and fabrication of catalysts for high-performance artificial photosynthesis. © 2025 Elsevier B.V.