Photocatalytic Co‐Reduction of N₂ and CO₂ with CeO₂ Catalyst for Urea Synthesis

Abstract

The effective conversion of carbon dioxide (CO2) and nitrogen (N2) into urea by photocatalytic reaction under mild conditions is considered to be a more environmentally friendly and promising alternative strategies. However, the weak adsorption and activation ability of inert gas on photocatalysts has become the main challenge that hinder the advancement of this technique. Herein, we have successfully established mesoporous CeO2‐x nanorods with adjustable oxygen vacancy concentration by heat treatment in Ar/H2 (90%:10%) atmosphere, enhancing the targeted adsorption and activation of N2 and CO2 by introducing oxygen vacancies. Particularly, CeO2‐500 (CeO2 nanorods heated treatment at 500 °C) revealed high photocatalytic activity toward the C‐N coupling reaction for urea synthesis with a remarkable urea yield rate of 15.5 μg/h. Besides, both aberration corrected transmission electron microscopy (AC‐TEM) and Fourier transform infrared (FT‐IR) spectroscopy were used to research the atomic surface structure of CeO2‐500 at high resolution and to monitor the key intermediate precursors generated. The reaction mechanism of photocatalytic C‐N coupling was studied in detail by combining Density Functional Theory (DFT) with specific experiments. We hope this work provides important inspiration and guiding significance towards highly efficient photocatalytic synthesis of urea.

Sulfur Migration Enhanced Proton-Coupled Electron Transfer for Efficient CO2 Desorption with Core-Shelled C@Mn3O4

“…After sulfur migration, a new peak assigned to sulfated O species appeared at 533.3 eV, resulting in a 0.2 eV shift to lower energy of O α and O β . Meanwhile, the proportion of O β significantly decreased by 38.7%, indicating that migrated S species preferred to absorb at lattice oxygen with the formation of S–O–Mn bonding . The XPS signal of Mn 2p 3/2 could be divided into three peaks at 643.2, 642.0, and 641.0 eV, assigned to the Mn 4+ , Mn 3+ , and Mn 2+ species, respectively (Figure f) .…”

“…Meanwhile, the proportion of O β significantly decreased by 38.7%, indicating that migrated S species preferred to absorb at lattice oxygen with the formation of S−O−Mn bonding. 42 The XPS signal of Mn 2p 3/2 could be divided into three peaks at 643.2, 642.0, and 641.0 eV, assigned to the Mn 4+ , Mn 3+ , and Mn 2+ species, respectively (Figure 3f). 43 After reacting in sulfated MEA solution, the Mn 2p band of the catalyst showed a transformation from Mn 3+ to Mn 4+ and Mn 2+ , with the intensity of Mn 3+ decreasing by 32.5%.…”

Nitrate Reduction by NiFe-LDH/CeO2: Understanding the Synergistic Effect between Dual-Metal Sites and Dual Adsorption

“…Due to the special electron acceptor properties of Fe 2+ and Ce 3+ , Fe 2+ and Ce 3+ in NiFe-LDH/CeO 2 can be inferred as dual-metal catalytic sites in EC-NITRR. , Meanwhile, N 2 -TPD spectra revealed that NiFe-LDH/CeO 2 also has excellent activation ability for nitrogen (Figure S14). − Compared with CeO 2 , the NH 3 yield of Ni-LH/CeO 2 decreased, leading us to speculate that Ni 2+ is not the catalytic active site for NO 3 – . In addition, the NH 3 selectivities of CeO 2 , Fe-LH/CeO 2 , and NiFe-LDH/CeO 2 increased sequentially, which may be attributed to the strong adsorption effect of Ni 2+ and Fe 3+ on hydrogen radicals in NiFe-LDH/CeO 2 , promoting the hydrogenation reaction of intermediates.…”

Modularization of Regional Electronic Structure over Defect-Rich CeO2 Rods for Enhancing Photogenerated Charge Transfer and CO2 Activation

“…Moreover, an anion-inducing strategy, electrodeposition techniques, and solid metal reduction processes were used to design new CeO 2 photocatalysts with abundant OVs and improved photocatalytic performance. In various cases, as depicted in Figure a, OV defects at increasing concentrations in photocatalysts show a high optical absorption capacity along with a strong carrier recombination rate, hindering the transfer of the generated charge carriers and inhibiting photocatalytic activity. ,,, Therefore, an effective solution for coordinating the contradiction between the formation and transfer of photogenerated charge carriers in defect-rich semiconductors is a great challenge in achieving advanced photocatalytic materials.…”

“…Ceria (CeO 2 ) as a star material in catalysis can release and/or store oxygen due to the valence-convertible Ce 3+ /Ce 4+ cations, thus exhibiting excellent tunable properties for OV engineering. Transition metal ion doping is a traditional method for improving the utilization of photogenerated carriers by increasing the number of OV defects in CeO 2 . − Heat treatment in a reductive (H 2 , CO, etc.) or inert atmosphere (Ar, N 2 , etc.)…”