Photocatalytic CO₂-to-Ethylene Conversion over Bi₂S₃/CdS Heterostructures Constructed via Facile Cation Exchange

Solar-driven CO₂ conversion to multicarbon (C₂₊) products has emerged as a key challenge, yet this calls for a systematic investigation on the overall reaction process and mechanism at an atomic level based on the rational design of highly selective photocatalysts. Herein, we report the synthesis of compact Bi₂S₃/CdS heterostructures via facile cation exchange, by which a unique pathway of CO₂-to-C₂H₄ photoconversion is achieved. Specifically, the BCS-30 shows an optimal C₂H₄ production rate of 3.49 μmol h^-1 g^-1 based on the regulation of band structures and energy levels of photocatalysts by controlled growth of Bi₂S₃ at CdS surface. Both experimental and theoretical results (DFT calculations) identify Bi atoms as new catalytic sites for the adsorption of CO^* and formation of ^*CO-^*CO dimers that further hydrogenate to produce ethylene. Overall, this work demonstrates vast potentials of delicately designed heterostructures for CO₂ conversion towards C₂₊ products under mild photocatalytic conditions.