Confined bismuth single atoms and nanoparticles dual-sites constructed via reverse etching for CO2 photoreduction to CH4.

• Bi single atoms and nanoparticles dual-sites are presented on TiO 2 for the first time. • A reverse etching route was firstly used to achieve confined dual-sites. • The porous dual-Bi/TiO 2 catalyst achieves a CH 4 generation rate of 103.89 μmol·g−1·h−1 with an impressive selectivity of 96.87 %. Synchronizing the directional photogenerated transfer of electrons and regulating the CO 2 photocatalytic reduction process are key to achieving the efficient and highly selective photocatalytic reduction of CO 2. The design of highly-dispersed active sites and the efficient collaboration of multiple sites are of great importance in attaining the above target. Herein, a reverse etching route was first proposed to confine Bi single atoms and nanoparticles as dual-sites for assisting CO 2 photoreduction on TiO 2 , avoiding the mutual masking of the active sites. The Synergism of the dual-sites achieves the hydrodeoxygenation of * COOH and ushers the directional conversion of CO 2 to CH 4. Highly dispersed single Bi atoms could induce the transfer of photogenerated electrons, enhance CO 2 absorption, and further provide active sites for reducing CO 2 to *COOH intermediates. Besides, appropriate Bi nanoparticles could promote the separation and transfer of photogenerated and inhibit the formation of hydroxyl groups; more importantly, they could promote the release of protons, which would further accelerate the conversion of *COOH to CH 4. After being integrated, the optimized dual-Bi/TiO 2 catalyst achieves a CH 4 generation rate of 103.89 μmol·g−1·h−1 with an impressive selectivity of 96.87 % as well as remarkable durability for photocatalytic CO 2 reduction. This work provides new insights into developing robust catalysts through the artful design of synergistic catalytic sites for efficient photocatalytic CO 2 conversion. [ABSTRACT FROM AUTHOR]