Synergistic Carbon Encapsulation and Silver Decoration Enable Durable and Selective CO₂-to-Ethylene Conversion on...

Chemical alterations in metal oxides during manipulation greatly diminish their potential in artificial photosynthesis. Clarifying and overcoming these changes is crucial for realizing the sustainable generation of solar fuels and chemicals. Here, employing multimodal operando techniques, we elucidated the degradation mechanism of copper oxide (CuO_x) photocathodes under operational conditions, revealing an electron-mediated reductive photocorrosion pathway: Cu₂O/CuO → Cu₂O → Cu. These key findings led us to engineer an ultrathin carbon layer encapsulation strategy formed via electrodeposition-coupled self-assembly of carbon nanodots. This protective layer enables efficient photoelectron extraction and spatial isolation. The resulting CuO_x@C exhibits gratifying durability with unaltered phases and steady photocurrent throughout extended operation exceeding 24 h. To enhance activity and selectivity toward ethylene, Ag nanoparticles were integrated onto CuO_x@C. The Ag decoration enhances CO₂ adsorption, stabilizes *CO intermediate, and facilitates the crucial *CO-*CO coupling. The Faraday efficiency for CO₂-to-ethylene conversion on CuO_x@C/Ag reaches up to ~66.4% and retains ~95% of its initial performance after prolonged use. This synergistic strategy of carbon encapsulation and metal decoration exhibits broad applicability, as validated by CuO_x@C/Ru, CuO_x@C/Pd, and BiVO₄@C/Pt. Our work provides a universal design framework for efficient and durable photoelectrodes, accelerating their transition from laboratory prototypes to scalable technologies.