Selenium Single Atom in One-Dimensional Phosphorus Allotrope Lattice with the (-10-1) Plane to Significantly Enhance CO2 Adsorption and C−C Coupling

Phosphorus has various crystallographic structures and variable phosphorus-derived structures, which have attracted much attention due to its unique properties. One-dimensional phosphorus structures with atomic substitution in the phosphorus lattice are extremely favored due to their high specific surface area and stable single-atom dispersion. The precise crystal structures and single atomic substitution positions are crucial factors to understand the mechanism of single-atom effects but remain a big challenge. Herein, single crystals composed of 1D zigzag linear phosphorus selenium chains (ZLP-Se) have been produced and characterized by SC-XRD to be P18.56Se1.44 with a space group of Pnma (CSD-2348033). The exact Se substitution positions were further ascertained by calculations of the whole thermodynamic stability phase diagram to have three types of substitution patterns (Se1/P1 mixed occupied positions with intervals of 3Se+2P, 1Se+4P, and 1Se+1P+1Se+2P). The selenium-rich crystal plane (-10-1) has been demonstrated to significantly enhance CO2 adsorption and C−C coupling to obtain ethylene (C2H4). A high photocatalytic CO2 reduction performance (18.0 μmol g−1 h−1, 97.0% electron selectivity for C2H4) has been achieved by the ZLP-Se with the Ag cocatalyst. The adsorption of CO2* and CO* was found to be much stronger on the Se-rich surface of ZLP-Se. The CO* intermediates were found to be energetically favored for protonation and subsequent asymmetrical C−C coupling to produce C2H4, with COCHO* intermediates detected by in situ DRIFTS. The electron was also demonstrated by in situ XPS to transfer from Se and Ag to P under Xe lamp irradiation, confirming the electronic localization effect of ZLP-Se to yield C2H4.