Electrocatalytic urea synthesis through N₂ + CO₂ coreduction and C–N coupling is a promising and sustainable alternative to harsh industrial processes. Despite considerable efforts, limited progress has been made due to the challenges of breaking inert N≡N bonds for C–N coupling, competing side reactions, and the absence of theoretical principles guiding catalyst design. In this study, we propose a mechanism for highly electrocatalytic urea synthesis using two adsorbed N₂ molecules and CO as nitrogen and carbon sources, respectively. This mechanism circumvents the challenging step of N≡N bond breaking and selective CO₂ to CO reduction, as the free CO molecule inserts into dimerized *N₂ and binds concurrently with two N atoms, forming a specific urea precursor *NNCONN* with both thermodynamic and kinetic feasibility. Through the proposed mechanism, Ti₂@C₄N₃ and V₂@C₄N₃ are identified as highly active catalysts for electrocatalytic urea formation, exhibiting low onset potentials of −0.741 and −0.738 V, respectively. Importantly, taking transition metal atoms anchored on porous graphite-like carbonitride (TM₂@C₄N₃) as prototypes, we introduce a simple descriptor, namely, effective d electron number (Φ), to quantitatively describe the structure–activity relationships for urea formation. This descriptor incorporates inherent atomic properties of the catalyst, such as the number of d electrons, the electronegativity of the metal atoms, and the generalized electronegativity of the substrate atoms, making it potentially applicable to other urea catalysts. Our work advances the comprehension of mechanisms and provides a universal guiding principle for catalyst design in urea electrochemical synthesis.

中文翻译：

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通过 N2 二聚和通用描述符的电催化尿素合成

_{通过 N 2} + CO ₂共还原和 C-N 偶联的电催化尿素合成是严酷工业过程的一种有前途且可持续的替代方案。尽管付出了巨大的努力，但由于 C-N 偶联中打破惰性 N=N 键、竞争性副反应以及缺乏指导催化剂设计的理论原理等挑战，取得的进展有限。_{在这项研究中，我们提出了一种使用两个吸附的N 2}分子和CO分别作为氮源和碳源的高电催化尿素合成机制。_{该机制规避了 N−N 键断裂和选择性 CO 2}还原为 CO的挑战性步骤，因为游离 CO 分子插入二聚化 *N ₂并同时与两个 N 原子结合，形成具有热力学和热力学特性的特定尿素前体 *NNCONN*和动力学可行性。通过所提出的机制，Ti ₂ @C ₄ N ₃和V ₂ @C ₄ N ₃被认为是电催化尿素形成的高活性催化剂，分别表现出-0.741和-0.738 V的低起始电位。重要的是，以锚定在多孔石墨类碳氮化物（TM ₂ @C ₄ N ₃）上的过渡金属原子为原型，我们引入了一个简单的描述符，即有效d电子数（Φ），来定量描述尿素形成。该描述符结合了催化剂固有的原子特性，例如 d 电子的数量、金属原子的电负性和基质原子的广义电负性，使其可能适用于其他尿素催化剂。我们的工作促进了对机制的理解，并为尿素电化学合成中的催化剂设计提供了通用指导原则。