Metal-Organic Frameworks Offering Tunable Binary Active Sites toward Highly Efficient Urea Oxidation Electrolysis

Abstract

Electrocatalytic urea oxidation reaction (UOR) is regarded as an effective yet challenging approach for the degradation of urea in wastewater into harmless N2 and CO2. To overcome the sluggish kinetics, catalytically active sites should be rationally designed to maneuver the multiple key steps of intermediate adsorption and desorption. Herein, we demonstrate that metal-organic frameworks (MOFs) can provide an ideal platform for tailoring binary active sites to facilitate the rate-determining steps, achieving remarkable electrocatalytic activity toward UOR. Specifically, the MOF (namely, NiMn0.14-BDC) based on Ni/Mn sites and terephthalic acid (BDC) ligands exhibits a low voltage of 1.317 V to deliver a current density of 10 mA cm-2. As a result, a high turnover frequency (TOF) of 0.15 s-1 is achieved at a voltage of 1.4 V, which enables a urea degradation rate of 81.87% in 0.33 M urea solution. The combination of experimental characterization with theoretical calculation reveals that the Ni and Mn sites play synergistic roles in maneuvering the evolution of urea molecules and key reaction intermediates during the UOR, while the binary Ni/Mn sites in MOF offer the tunability for electronic structure and d-band center impacting on the intermediate evolution. This work provides important insights into active site design by leveraging MOF platform and represents a solid step toward highly efficient UOR with MOF-based electrocatalysts.

Leveraging Metal Nodes in Metal–Organic Frameworks for Advanced Anodic Hydrazine Oxidation Assisted Seawater Splitting

“…Metal–organic frameworks (MOFs), which are made up of well-dispersed metal nodes and organic ligands, are a class of crystalline porous materials. , As their skeleton can serve as superior electron pathways and the ordered porous architecture facilitates ultrafast transport of reactants, products, and electrolytes, MOFs are regarded as star catalysts for various applications, including electrochemical energy storage and conversion . More importantly, the catalytic performance of MOFs can be optimized easily by tuning their topological structures and metal nodes. , Compared with conventional inorganic materials, MOFs with a tunable homogeneous microenvironment at the molecular level possess multiple advantages for practical catalysis. , An attractive option to develop efficient bifunctional electrocatalysts toward the HER and HzOR is to introduce noble-metal SA catalytic sites into a Ni-based MOF matrix. In most reported cases, however, MOFs were used as precursors/templates and calcined into porous carbon structures to support SA catalysts. , By doing so, the original structures of MOFs were destroyed, thereby losing the advantages mentioned above for MOFs.…”

“…29,30 Compared with conventional inorganic materials, MOFs with a tunable homogeneous microenvironment at the molecular level possess multiple advantages for practical catalysis. 31,32 An attractive option to develop efficient bifunctional electrocatalysts toward the HER and HzOR is to introduce noble-metal SA catalytic sites into a Ni-based MOF matrix. In most reported cases, however, MOFs were used as precursors/templates and calcined into porous carbon structures to support SA catalysts.…”

Fe Powder Catalytically Synthesized C3N3 toward High-Performance Anode Materials of Lithium-Ion Batteries

“…Correspondingly, the high-resolution C 1s spectra of the three samples (Figures S6b, S7b, and S8b) also showed an extra C–N peak. In the meantime, the high-resolution O 1s spectra of the three samples (Figures S6d, S7d, and Figure S8d) also showed a second peak with a higher binding energy, which can be attributed to the adsorbed water. − The higher the reaction temperature of the sample, the stronger the intensity of this peak. It is because the increase of the specific surface areas and pores allows more water molecules to enter the sample.…”

Three-dimensional Ni4O4-cubane metal–organic framework as a high-performance electrocatalyst for urea oxidation

“… 13 The electrochemical stability of MOF 1 is compared to that of other Ni-based electrocatalysts from the literature. The stability of MOFs such as Ni-MOF-0.5, 42 2D Ni-MOF, 43 Ni-MOF-100, 56 NiO@Ni-MOF, 48 NiMn 0.14 -BDC MOF, 57 and 3% CeO 2 /Ni-MOF has been documented. 58 LSV was undertaken after a long-term stability test.…”