Polyaniline-mediated interfacial electron modulation for durable and selective electroreduction of carbon dioxide to carbon monoxide over sulfur-doped zinc oxide.

Developing efficient noble-metal-free electrocatalysts for Electrocatalytic carbon dioxide reduction reaction (ECO2RR) is crucial for sustainable energy conversion, yet ZnO-based catalysts suffer from poor intrinsic conductivity and cathodic reduction-induced deactivation. Herein, a strongly coupled heterointerface is constructed between sulfur-doped ZnO (S-ZnO) and conductive polyaniline (PANI) via interfacial electronic engineering. Electron-donating PANI plays a dual role: it accelerates interfacial charge-transport kinetics, compensating the low conductivity of ZnO, and stabilizes Zn sites through ZnN coordination bonds, suppressing reductive deactivation. A series of S-ZnO/PANI composites with tunable interfacial electronic structures was fabricated by varying PANI loading. The optimal catalyst delivers a CO Faradaic efficiency of 92.03 ± 0.44% at -1.3 V vs. reversible hydrogen electrode, restrains the competing hydrogen evolution reaction (HER) below 7.87 ± 0.53%, affords a CO partial current density of -11.43 ± 0.05 mA cm-2, and operates stably for 16.5 h. Mechanistic studies reveal that electron donation from PANI to S-ZnO through ZnN bonds lowers the *COOH formation barrier, kinetically favoring CO2 reduction over HER. The three-dimensional conductive network, enlarged electrochemically active surface area, and strong anchoring effect of PANI synergistically enhance charge transport, active-site exposure, and structural stability. This work validates combining electron-donor support engineering with doping synergy for noble-metal-free ECO2RR catalysts.