Abstract
The co-electrolysis of CO2 and NO3 - to synthesize urea has become an effective pathway to alternate the conventional Bosch-Meiser process, while the complexity of C-/N-containing intermediates for C-N coupling results in the urea electrosynthesis of unsatisfactory efficiency. In this work, an electronic spin state modulation maneuver with oxygen vacancies (Ov) is unveiled to effectively meliorate the oriented generation of key intermediates *NH2 and *CO for C-N coupling, furnishing urea in ultrahigh yield of 2175.47µg mg-1h-1 and Faraday efficiency of 70.1%. Mechanistic studies expound that Ov can induce the conversion of the high-spin state Ni2+ (t2g 6eg 2) of Ni@CeO2-x to the low-spin state Ni3+ (t2g 6eg 1), which markedly enhances the hybridization degree of the Ni 3d and the N 2p orbitals of *NO, facilitating the selective formation of *NH2. Notably, the in situ generated *NH2 intermediates can serve as a localized proton donor to promote the electroreduction of CO2 on the adjacent site Ce3+-O to exclusively afford *CO, followed by C-N coupling of each other to efficiently synthesize urea. The strategy of tailored switching of the active site spin state provides a reliable reference to rectify the electronic structure of electrocatalysts for directional CO2 valorization.
Published Version
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