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

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 CO₂ 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 Ag₂S, resulting in a V_S-rich, highly active catalyst: Ag₂S/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 Ag₂S/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 CO₂ reduction reaction, thereby enhancing catalytic activity.