Bipolar system induced surface electronic localization of violet phosphorene for CO₂ photoreduction to ethylene

The photocatalytic CO₂ reduction (CO₂RR) to high-value-added chemicals such as ethylene (C₂H₄) is desirable but challenging, due to the easy desorption of C₁ intermediates and insufficient CC coupling to C₂ intermediates. The CO₂RR performance of violet phosphorus (VP) could be significantly altered by its electronic configurations, especially for C₂H₄ selectivity. Herein, the effective electronic localization engineering of VP has been achieved by a well spatially dispersed dual-cocatalyst modification (VP-PA-Co₂P-Ag). The well distributed Co₂P nanoflocs modification on VP were realized by prefunctionalization treatment of VP with phytic acid (PA). The metallic Co₂P and Ag were found to serve as bipolar system to induce more efficient surface electronic localization of VP and electronic enrichment on Co sites. The adsorption and activation of CO₂, absorption and coupling of intermediates (CO^⁎, CHO^⁎), and separation dynamics of photogenerated carriers have been demonstrated to be enhanced due to the significant orbital hybridization between CO₂ and Co 3d, which owing to the electronic localization on Co sites. Therefore, the CC coupling activity and selectivity on VP-PA-Co₂P-Ag has been demonstrated to be enhanced significantly to achieve 14.6 μmol g^-1 h^-1 and 69.9% electron selectivity of C₂H₄ without any hole-sacrificial agent. The selective photocatalytic CO₂-to-C₂H₄ mechanism has been explored by in-situ diffuse reflectance infrared Fourier-transform, in-situ X-ray photoelectron spectroscopy, femtosecond ultrafast transient absorption, density of states, and Gibbs free-energy profiles, where the CO^⁎ intermediates could be easily adsorbed for protonation (CHO^⁎) and further CC coupling (COCHO^⁎), continuously reduced by successive proton-coupled multielectron transfer process to yield C₂H₄.