Highly efficient utilization of single atoms via constructing 3D and free-standing electrodes for CO₂ reduction with ultrahigh current density

Single-atom catalysts have great potential in electrochemical CO₂ reduction reaction (CO₂RR); however, plenty of single-atom sites are embedded inside without catalytic performance and most catalysts are powder-based with binding procedure, causing a relatively low current density. Herein, a strategy is proposed to maximize the utilization of single-atom cobalt sites via constructing a free-standing, cross-linked and high-yield carbon membrane (denoted as CoSA/HCNFs). The 3D net-like CoSA/HCNFs nanofibers with continuous porous structure can facilitate large electrochemical active surface areas and be in favor of the reactant transportation, which generate abundant effective cobalt single atoms for CO₂ reduction. The highly utilization of single-atom Co sites eventually lead to CO with 91% Faradaic efficiency and 67 mA cm⁻² current density in a typical H-type cell, 92% Faradaic efficiency as well as 211 mA cm⁻² current density in a flow cell, respectively. This strategy for large-scale production of single-atom membranes could also be easily expanded to extensive electrolysis and energy storage devices.