3D bionic reactor optimizes photon and mass transfer by expanding reaction space to enhance photocatalytic CO2 reduction

• 3D printed bionic palisade cell improves the photocatalytic efficiency by adjusting the photon and mass transfer of macro structure. • The interface electric field of p-n heterojunction inhibit the recombination of photogenerated carrier. • COOH* is important intermediates in photocatalytic CO 2 reduction. Use of 3D photocatalytic reactor has been widely explored for development of efficient photocatalytic systems. In the present study, a bionic palisade cells BiOBr/Sr 2 Nb 2 O 7 /Al 6 Si 2 O 13 photocatalytic reactor with high strength was prepared through combination of 3D printing technology and solvothermal method. The carefully designed and optimized bionic palisade cell structure exhibited a periodic porous structure with high surface area. The controllable periodic structure effectively regulated the internal photon transfer and mass transfer. Photon transfer ensured that light is fully scattered within the structure, which improved light utilization. High mass transfer ensured smooth flow of reactant inside the structure, which increased reactant adsorption on the surface of photocatalysts. The interface electric field of the BiOBr/Sr 2 Nb 2 O 7 p-n heterojunction effectively separated the photogenerated electrons and holes. The BOB/SNO/ASO structure had high photocatalytic CO 2 reduction performance under the simulated sunlight. The CO yield for the reaction was 13.68 μmol/g/h, whereas that of CH 4 yield was 6.37 μmol/g/h. Therefore, the findings of the present study provide a basis for design and preparation of high-performance 3D photocatalytic reactors.