Overcoming Mass Transfer Barriers: Polypyrrole‐Induced Ag ₂ S Sulfur Vacancies Synergize with Carbon Aerogel for Efficient CO ₂ Reduction to CO

Abstract Compared to pure metals, metal sulfides offer cost‐effectiveness and high product selectivity. And the sulfur vacancies (V S ) introduced in sulfides can serve as active sites and promote CO 2 adsorption and activation. Therefore, using a chitosan‐derived carbon aerogel (CA) as the support, its surface is modified with polypyrrole (PPy). The surface‐bound PPy induces V S generation in the loaded Ag 2 S, resulting in a V S ‐rich, highly active catalyst: Ag 2 S/PPy/CA. The presence of V S significantly increases the electrochemically active surface area (ECSA). The catalyst exhibits high catalytic activity and CO selectivity across a broad potential range of −0.9–−1.2 V (vs RHE), achieving a maximum Faradaic efficiency for CO (FE CO ) of 94.5%. Experimental results demonstrate that V S reduces electrochemical impedance, significantly increases current density, and, together with the 3D porous CA network, substantially weakens mass‐transfer limitations, thus improving catalytic efficiency. The intrinsically hydrophobic CA and PPy jointly regulate the hydrophobicity of Ag 2 S/PPy/CA. It maintains a highly hydrophobic state before and after the catalytic reaction, indicating excellent stability. Furthermore, the stable hydrophobicity is verified in a flow cell to enhance the catalytic performance, demonstrating high catalytic activity even at high current densities. Mechanistic studies reveal that V S promotes electron gain by the * COOH intermediate to form * CO, directing more electrons toward the CO 2 reduction reaction, thereby enhancing catalytic activity.