Local CO2 Transport Control Boosts CO-Rich Syngas Electrosynthesis

The electrochemical CO 2 reduction reaction (eCO 2 RR) provides a sustainable route for producing high value-added syngas through renewable electricity. Nevertheless, the low solubility of CO 2 and the competing hydrogen evolution reaction in eCO 2 RR systems often restrict product selectivity and conversion efficiency. In this study, we propose a microenvironment engineering strategy by incorporating hydrophobic SiO 2 aerogel into Ag nanoparticle (NP) catalysts to enhance reaction kinetics. Experimental results demonstrate that the Ag NPs/20 wt.% SiO 2 -300 electrode delivers a peak CO Faradaic efficiency (FE CO ) of 85.7% at −1.5 V vs. Ag/AgCl in an H-cell, marking a 71.0% improvement compared to the bare Ag NP electrode (50.1%). In-situ Fourier-transform infrared spectroscopy verifies a *COOH-mediated reaction pathway, where the modified catalyst surface promotes intermediate enrichment due to enhanced mass transport. Furthermore, the membrane electrode assembly reactor equipped with the Ag NPs/20 wt.% SiO 2 -300 cathode maintains high FE CO (79.2% to 88.7%) across a broad current range (25 to 150 mA cm −2 ). The CO/H 2 ratio can be precisely adjusted by varying the applied current density, allowing tailored syngas production. This study highlights the pivotal role of hydrophobic microenvironments in modulating product selectivity and presents a scalable method for designing gas diffusion electrodes suitable for industrial eCO 2 RR applications.