Silver is an attractive catalyst for converting CO 2 into CO. However, the high CO 2 activation barrier and the hydrogen evolution side reaction seriously limit its practical application and industrial perspective. Here, an ordered Ag nanoneedle array (Ag-NNAs) was prepared by template-assisted vacuum thermal-evaporation for CO 2 electroreduction into CO. The nanoneedle array structure induces a strong local electric field at the tips, which not only reduces the activation barrier for CO 2 electroreduction but also increases the energy barrier for the hydrogen evolution reaction (HER). Moreover, the array structure endows a high surface hydrophobicity, which can regulate the adsorption of water molecules at the interface and thus dynamically inhibit the competitive HER. As a result, the optimal Ag-NNAs exhibits 91.4% Faradaic efficiency (FE) of CO for over 700 min at −1.0 V vs RHE. This work provides a new concept for the application of nanoneedle array structures in electrocatalytic CO 2 reduction reactions.

Electrocatalytic N 2 reduction reaction (eNRR) provides a promising carbonneutral and sustainable ammonia-synthesizing alternative to the Haber-Bosch process. However, the nonpolar N 2 has significant thermodynamic stability and requires ultrahigh energy to break down the N�N bond. Here, we report the construction of local enhanced electric fields (LEEFs) by Ag nanoneedle arrays to promote N�N fracture thus assisting the eNRR. The LEEFs could induce charge polarization on nitrogen atoms and reduce the energy barrier in the N 2 first-protonation step. The detected N�N and N�H intermediates prove the cleavage of the N�N bond and the hydrogenation of N 2 by LEEFs. The increased LEEFs lead to logarithmic growth rates for the targeted eNRR and exponential growth rates for the unavoidable competitive hydrogen evolution reaction. Thus, regulation and tuning of LEEFs to ∼4 × 10 4 kV m −1 endows the raise of eNRR to the summit, achieving high ammonia selectivity with a Faradaic efficiency of 72.3 ± 4.0%.

With increasing CO2 emission and energy scarcity, electrocatalytic CO2 reduction reaction (CO2RR) offers an attractive solution for CO2 resource utilization using sustainable electrical energy. Ag‐based catalysts with high‐curvature nanoneedle structure exhibit the potential to achieve high CO2RR activity, but suffer from insufficient stability due to the vulnerability of the high‐curvature structure during CO2RR. Herein, the uniform porous Zn conformal coating on high‐curvature dendritic Ag nanoneedles (AgNNs@Zn) by vacuum thermal evaporation is prepared. As the surface sacrificial shell, the dissolution and reconstruction of Zn protect the inner Ag core, thus enhancing the CO2RR stability of AgNNs@Zn. The concentration of Ag+ in the electrolyte after 2 h CO2RR electrolysis markedly reduces from 2.4 ug L−1 in AgNNs to 1.4 ug L−1 in AgNNs@Zn. Moreover, the DFT calculation reveals that the constructed Ag–Zn interfaces can stabilize the *COOH intermediates, which promote the selectivity of CO2 reduction into CO. As a result, the optimized AgNNs@Zn catalyst exhibits the FECO of ≈91% at −0.86 V versus RHE in H‐cell, and FECO of 90% at 100 mA cm−2 above 12 h in flow cell. This work provides a feasible strategy to synthesize bimetallic catalysts with core–shell structure for better CO2RR performance.