Highly Selective Photocatalytic CO2 Reduction to C2H6 via Nanocluster-Single Atom-Vacancy on Ceria: Synergistic Mechanism and Orbital Effects

The photocatalytic reduction of CO2 to high-value C2 products involves sluggish multiple proton–electron couplings, resulting in low efficiency and selectivity. This study demonstrates that palladium (Pd) single-atom (PdSA)- and Pd nanocluster (PdNCs)-loaded CeO2 with abundant oxygen vacancies (Ov) synergistically enhance photocatalytic CO2-to-ethane (C2H6) conversion effectively and selectively. The PdSA+NCs/CeO2 photocatalyst achieves 80.4% electron selectivity for C2H6 production with an electron consumption rate of 206.3 μmol gcat–1 h–1 in pure water, representing a 172.4-fold enhancement over pristine CeO2. PdNCs interact with neighboring PdSA and Ov to form a Fermi level with the continuous characteristics of discrete energy levels, improving the charge distribution in local spatial electric fields. This enhancement favors electron migration from the π to σ orbital of COCO*, promoting C–C coupling. Our findings provide new insights to rationally design synergistic interactions between SA, NCs, and Ov to achieve high selectivity toward C2 products.