# Phyto‐Confined CeOx with Synergistic Lattice Distortion and Oxygen Vacancies Drives Efficient Urea Electrosynthesis

## TL;DR

A new catalyst made of cerium oxide nanoparticles in carbon helps efficiently produce urea from CO2 and nitrates by lowering energy barriers and improving reaction selectivity.

## Contribution

Introduces lattice-distorted CeOx with oxygen vacancies in a carbon framework to enable efficient urea electrosynthesis via structural modulation.

## Key findings

- Contracted Ce─O bonds stabilize oxygen vacancies and create electron reservoirs for multi-electron transfer.
- C-N coupling energy barrier is drastically reduced to 0.18 eV, enabling selective urea synthesis.
- Porous carbon framework improves catalyst durability and active site accessibility over 100 hours.

## Abstract

Electrocatalytic urea synthesis from carbon dioxide and nitrates is hindered by sluggish multi‐electron kinetics and unclear C‐N coupling mechanism. Herein, lattice‐distorted CeOx nanoparticles are introduced with abundant oxygen vacancies (OV), confined within a porous carbon framework (d‐CeOx/PC), fabricated via a phyto‐hyperaccumulation confinement strategy. Precise structural modulation induces ultrasmall (≈2 nm), uniformly dispersed, contracted Ce─O bonds (≈2.29 Å) and creates a highly active environment for urea electrosynthesis. In situ ATR‐FTIR spectroscopy identifies key intermediates, confirming C‐N coupling pathway. Theoretical calculation reveals contracted bonds strengthen Ce 4f‐O 2p orbital hybridization, restricting lattice oxygen (OL) migration and slowing OV diffusion/annihilation. Simultaneously, bond contraction induces localized electron redistribution around OV. These OV promote mixed Ce3+/Ce4+ valence, while the highly covalent, contracted Ce─O bonds stabilize Ce3+, forming localized “electron reservoirs” for flexible multi‐step electron transfer. These synergistic effects enhance reactant (CO2/NO3
−) adsorption, stabilize key intermediates (*CO/*NO), and drastically lower the C‐N coupling energy barrier (*NO+*CO→*OCNO, 0.18 eV), while suppressing competing hydrogenation pathways to byproducts. The porous carbon framework further improves durability (>100 h) and active site accessibility. This reduction in C‐N barrier, identified as the key kinetic descriptor enabled by structural modulation, provides mechanistic insight for designing catalysts for sustainable urea production from waste.

Lattice‐distorted CeOx nanoparticles with abundant oxygen vacancies, confined in porous carbon (d‐CeOx/PC), enable efficient electrocatalytic urea synthesis from CO2 and NO3
−. Contracted Ce─O bonds (≈2.29 Å) stabilize OV, creating electron reservoirs for flexible multi‐electron transfer. This synergistically enhances reactant adsorption, stabilizes intermediates, and drastically lowers the C‐N coupling barrier (*NO+*CO→*OCNO, 0.18 eV), enabling selective urea synthesis.