Reactive CO2 capture electrolysis at low voltage and high single-pass conversion enabled by ultra-low loading molecular catalyst

We demonstrate a high-efficiency reactive CO 2 capture electrolysis system, utilizing ultra-low loading CoPc/CNT catalysts. By achieving 55.1% single-pass conversion and reducing voltage by 30%, this integrated approach offers a low-cost, energy-saving pathway for sustainable carbon utilization. Integrating electrochemical CO 2 conversion with carbon capture extends the CO 2 source beyond pure or point-source streams. By directly interfacing with capture units, reactive CO 2 capture electrolysis circumvents the energy-intensive regeneration and compression processes to supply pure CO 2 stream, also minimizes the amount of unreacted CO 2 through gas-fed CO 2 electrolysis. However, the conversion pathway is hampered by high electrolyser voltages and reliance on precious and thick metal catalysts (> 2.0 mg cm −2 ). Here, we report an energy-efficient reactive CO 2 capture electrolysis system enabled by an ultra-low loading molecular catalyst (cobalt phthalocyanine anchored onto multi-walled carbon nanotubes, CoPc/CNT). When the CoPc/CNT exceeds 0.2 mg cm −2 loading on cathode, the thicker CoPc/CNT layer largely increase electrical and mass transfer resistances. This limits the availability of local CO 2 at the catalyst surface, suppressing the formation of adsorbed intermediates (COOH*/CO*) on cobalt centres, as observed by operando Raman spectroscopy. Benefiting from the features, the electrolysis system achieves a single-pass CO 2 conversion of 55.1% at 300 mA cm −2 and a faradaic efficiency of CO (FE CO ) 84.7% at a 0.2 mg cm −2 . At 100 mA cm −2 , the synergistic combination of CoPc/CNT with a two-layer membrane architecture reduces electrolyser voltage by 30% to widely used bipolar membrane (BPM)-incorporated electrolyser and 17% voltage to metal catalyst-based cathode. This study offers a cost-effective molecular catalyst for reactive CO 2 capture electrolysis and paves the way for energy-efficient carbon capture and utilisation integrated systems.