Unraveling How Local Environments Impact Multicarbon Product Electrosynthesis in Active Carbon Solutions

The direct electrochemical conversion of bicarbonate electrolytes presents the potential to produce carbon-neutral chemical commodities without suffering energy-intensive ex situ carbon dioxide (CO2) regeneration. However, selectively producing multicarbon (C2+) products in bicarbonate electrolyzers is challenging. In this work, we improved the selectivity toward C2+ products using carbon-supported Cu2O-derived Cu (OD-Cu/C) catalysts by altering the carbon fraction, catalyst mass loading, and KHCO3 concentration. On a Cu2O/C precatalyst with 10 wt % C (Cu2O/10 wt % C) and a 0.5 ± 0.1 mg cm–2 mass loading, we achieved here a C2+ product Faradaic efficiency (FE) of ∼31 ± 5% at 100 mA cm–2 in 0.1 M KHCO3. We reported a C2+ FE of ∼48% at 60 mA cm–2. A one-dimensional (1D) continuum model reveals that the bicarbonate concentration and catalyst layer porosity contribute to modulating the local environment. Matching the buffer capacity, bicarbonate availability, and carbonate transport is essential for achieving high-performance bicarbonate-to-C2+ reduction.