Oxygen vacancy engineering in ZnO/PPy composites for enhanced electrocatalytic carbon dioxide reduction to synthesis gas

Oxygen vacancy (V O ) engineering is an effective strategy for enhancing the performance of electrocatalytic CO 2 reduction (eCO 2 RR) to CO. In this study, composite materials of zinc oxide (ZnO) and polypyrrole (PPy) were prepared via in situ polymerization, with the V O concentration precisely controlled by adjusting the PPy molar ratio. The V O concentration first increased and then decreased as the PPy content decreased, while the zinc vacancy (V Zn ) concentration exhibited an opposite trend. Characterization results indicate that the PPy conjugated framework dynamically regulates the V O /V Zn concentration through electron injection, and its controllable hydrophobicity enhances CO 2 mass transfer and interfacial enrichment. Crucially, experiments reveal that a high V O concentration is key to achieving high performance, as V O reduces the activation energy barrier for C O bond cleavage through charge redistribution, synergistically optimizing the adsorption energy of the *COOH intermediate. Density functional theory calculations confirm that Vo regulates the d-band center position of ZnO and reduces the activation energy barrier for CO 2 activation. The optimal sample, V O -enriched ZnO/PPy-4, achieves an FE CO of 73.8 % at −1.6 V (vs. RHE) and stably maintains CO/H 2 ratio of 2:1 at −1.2 V (vs. RHE), with < 5 % decay rover 8 h. This study demonstrates a strategy for obtaining high-performance electrocatalytic CO 2 reduction catalysts by regulating Vo concentration.