Pd Intercalation in BiOCl Nanosheets Promotes Ambient Electrosynthesis of Urea: Operando Study by Synchrotron X-ray...

Electrochemical urea synthesis offers an energy-efficient route for converting CO₂ and NO₃^- into a high-demand nitrogen commodity. However, urea selectivity hinges on orchestrating the coformation and interfacial coupling of CO₂-derived *CO_x and N-reduction *NH_x intermediates. Consequently, achieving high urea rates and Faradaic efficiencies requires optimized catalyst designs. Here, we engineered 2D BiOCl nanosheets with Pd⁰ to promote C-N coupling while suppressing H₂ evolution and Bi⁰ segregation under negative potentials. We hydrothermally synthesized BiOCl and Pd-containing BiOCl nanosheets, both of which serve as electrocatalysts for the electrosynthesis of urea. Structural characterization confirmed that the Pd species are intercalated Pd⁰ sub-nm clusters within the interlayers of the BiOCl nanosheets. The maximum Faradaic efficiency for urea reached 12.43 ± 1.02% over Pd-BiOCl and 6.99 ± 1.62% over BiOCl at -0.30 V vs RHE. Operando experiments were conducted using synchrotron powder X-ray diffraction and X-ray absorption spectroscopy, enabling real-time observation of phase transitions and local coordination environments. These results revealed that CO₃^2- intercalation occurred in both BiOCl and Pd-BiOCl nanosheets, leading to the formation of Bi₂O₂CO₃. However, the layered framework of the nanosheets cracked at -0.5 V or at more negative potentials as Bi⁰ segregated and aggregated into nanoclusters. In contrast, BiOCl nanosheets with intercalated Pd⁰ subnm clusters avoided this issue over the range -0.1- -0.5 V. From these results, we conclude that intercalating Pd subnm clusters into BiOCl nanosheets stabilizes the layered framework, suppresses Bi⁰ segregation, lowers the charge-transfer resistance, and enhances anion exchange toward urea production within the BiOCl interlayers.