Precise CuO bond length engineering via alkaline-earth modulation breaks activity-stability trade-off in...

Electrocatalytic CO₂ reduction (CO₂RR) offers a promising route for carbon recycling and climate change mitigation. In this study, we develop a series of layered perovskite catalysts, La_1.9M_0.1CuO₄ (M = Ca, Sr, Ba), which exhibit significantly improved selectivity and stability for CO₂RR. Through systematic A-site substitution of La³⁺ (1.36 Å) with Ca²⁺ (1.30 Å), Sr²⁺ (1.40 Å) and Ba²⁺ (1.43 Å)，the CuO bond length is tuned from 1.98 Å (pristine La₂CuO₄) to 1.96 Å (Ca-doped), 2.02 Å (Sr-doped) and 2.04 Å (Ba-doped). Among these, La_1.9Sr_0.1CuO₄ (LSrCO) features an optimal elongation of the CuO bond that positions the d-band center at an optimal balance, being neither too far from nor too close to the Fermi level. This electronic configuration enhances the adsorption and activation of *CO intermediates while inhibiting the hydrogen evolution reaction (HER). It also lowers the energy barrier for *OCCO* formation, thereby promoting multi‑carbon product selectivity. The optimized LSrCO catalyst achieves a Faradaic efficiency of 78.23 % for ethylene (C₂H₄) at a partial current density of 199.48 mA cm^-2 (-1.2 V vs. RHE), representing a fivefold improvement in selectivity over pristine La₂CuO₄ (LCO). Moreover, LSrCO exhibits an eightfold enhancement in operational stability, maintaining performance over 120 h. This work outlines a general strategy for designing high-performance copper-based perovskite electrocatalysts and provides new design principles for efficient and durable CO₂ conversion.