High-curvature silver nanosheet arrays for exogenous-salt-free electroreduction of carbon dioxide in amine media.

Electrocatalytic conversion of amine-captured CO2 offers a promising route to bypass the energy-intensive thermal regeneration step, yet its efficiency is strongly limited by steric effects arising from the amine-rich electric double layer. While exogenous salts can alleviate this interfacial barrier, they introduce high salinity, operational complexity, and severe corrosion-related concerns that compromise the very advantage of capture-integrated systems. Here, we demonstrate that these limitations can be addressed through catalyst structure engineering, achieving high CO selectivity without exogenous salt addition under the tested conditions. A simple electrochemical reconstruction transforms planar Ag into three-dimensional flower-like Ag nanosheet arrays (Ag FHNSs) with defect-rich surface features and high-curvature edges. Finite-element analysis predicts stronger geometric field concentration at smaller nanosheet-edge radii, suggesting a possible curvature-associated electrostatic contribution, while the open architecture offers non-tortuous pathways for electrolyte access in the viscous absorbent. Because the actual interfacial electric field and electric-double-layer structure were not directly measured, this field effect is treated as an inferred possible contribution rather than an established mechanism. This catalyst achieves a CO Faradaic efficiency of 42.7% in 30 wt% monoethanolamine (MEA, 0.5 mol CO2/mol MEA) at -0.7 V versus the reversible hydrogen electrode (RHE) and room temperature, a 75-fold enhancement over planar Ag foil, and reaches 63.3% at 60 °C. This work establishes catalyst structure engineering as a viable and exogenous-salt-free alternative to additive-dependent approaches, offering a promising strategy for integrating CO2 capture with electroconversion.