Bimetallic NiCo Metal–Organic Frameworks with\nHigh Stability and Performance Toward Electrocatalytic Oxidation of\nUrea in Seawater

The\nurea oxidation reaction (UOR) is an alternative anodic reaction\nfor hydrogen generation via water splitting. The significance of UOR\nlies in both H<sub>2</sub> production and the decontamination of urea-containing\nwastewater. Commercial electrocatalysts in this field are generally\nbased on noble metals and show several limitations. Bimetal–organic\nframeworks (BMOFs) can be excellent candidates for the replacement\nof noble-metal-based catalysts beacuse of their promising features,\nsuch as a tunable structure, high surface area, and abundant sites\nfor electrocatalysis. In this study, a series of nickel–cobalt\nBMOFs (Ni<sub><i>x</i></sub>-Co<sub><i>y</i></sub>-BMOFs: <i>x</i> and <i>y</i> refer to a molar\nfraction of Ni and Co) were synthesized and applied as electrocatalysts\nin UOR. In particular, a Ni<sub>0.15</sub>Co<sub>0.85</sub>-MOF material\nwith a structure similar to that of its parent Co-MOF, revealed exceptional\nelectrocatalytic performance, as evidenced by low values of overpotential\n(1.33 V vs RHE at 10 mA cm<sup>–2</sup>), TOF (0.47 s<sup>–1</sup>), and Tafel slope (125 mV dec<sup>–1</sup>). At a 40 mA cm<sup>–2</sup> current density, Ni<sub>0.15</sub>Co<sub>0.85</sub>-MOF also showed excellent stability during the 72 h tests. This\nperformance of NiCo-BMOF can be assigned to the synergistic effect\nbetween Co and Ni, abundant active sites, porosity, and a tunable\nstructure, all of which result in an increased reaction rate due to\nthe acceleration of charge and mass transfers. Thus, the present work\nintroduces an efficient noble-metal-free UOR for energy generation\nfrom urea-based wastewater.