A surface reconstructing phenomenon is discovered on a defect‐rich ultrathin Pd nanosheet catalyst for aqueous CO₂ electroreduction. The pristine nanosheets with dominant (111) facet sites are transformed into crumpled sheet‐like structures prevalent in electrocatalytically active (100) sites. The reconstruction increases the density of active sites and reduces the CO binding strength on Pd surfaces, remarkably promoting the CO₂ reduction to CO. A high CO Faradaic efficiency of 93 % is achieved with a site‐specific activity of 6.6 mA cm⁻² at a moderate overpotential of 590 mV on the reconstructed 50 nm Pd nanosheets. Experimental and theoretical studies suggest the CO intermediate as a key factor driving the structural transformation during CO₂ reduction. This study highlights the dynamic nature of defective metal nanosheets under reaction conditions and suggests new opportunities in surface engineering of 2D metal nanostructures to tune their electrocatalytic performance.

中文翻译：

---

电催化二氧化碳还原过程中超薄钯纳米片的表面重建。

在富含缺陷的超薄钯纳米片催化剂上发现了一种表面重构现象，用于水性CO ₂电还原。具有主要（111）刻面位点的原始纳米片被转变为在电催化活性（100）位点中普遍存在的皱折片状结构。重建可增加活性位点的密度，并降低Pd表面上的CO结合强度，从而显着促进CO ₂还原为CO。当温度为6.6 mA cm ^-2时，CO的法拉第效率高达93％。在重建的50 nm Pd纳米片上有590 mV的中等超电势。实验和理论研究表明，CO中间体是驱动CO ₂过程中结构转变的关键因素减少。这项研究突出了有缺陷的金属纳米片在反应条件下的动力学性质，并提出了二维金属纳米结构表面工程中调节其电催化性能的新机会。