Manipulating\nTrimetal Catalytic Activities for Efficient\nUrea Electrooxidation-Coupled Hydrogen Production at Ampere-Level\nCurrent Densities

Replacing\nthe oxygen evolution reaction (OER) with the urea oxidation\nreaction (UOR) in conjunction with the hydrogen evolution reaction\n(HER) offers a feasible and environmentally friendly approach for\nhandling urea-rich wastewater and generating energy-saving hydrogen.\nHowever, the deactivation and detachment of active sites in powder\nelectrocatalysts reported hitherto present significant challenges\nto achieving high efficiency and sustainability in energy-saving hydrogen\nproduction. Herein, a self-supported bimetallic nickel manganese metal–organic\nframework (NiMn-MOF) nanosheet and its derived heterostructure composed\nof NiMn-MOF decorated with ultrafine Pt nanocrystals (Pt<sub>NC</sub>/NiMn-MOF) are rationally designed. By leveraging the synergistic\neffect of Mn and Ni, along with the strong electronic interaction\nbetween NiMn-MOF and Pt<sub>NC</sub> at the interface, the optimized\ncatalysts (NiMn-MOF and Pt<sub>NC</sub>/NiMn-MOF) exhibit substantially\nreduced potentials of 1.459 and −0.129 V to reach 1000 mA cm<sup>–2</sup> during the UOR and HER. Theoretical calculations\nconfirm that Mn-doping and the heterointerface between NiMn-MOF and\nPt nanocrystals regulate the d-band center of the catalyst, which\nin turn enhances electron transfer and facilitates charge redistribution.\nThis manipulation optimizes the adsorption/desorption energies of\nthe reactants and intermediates in both the HER and UOR, thereby significantly\nreducing the energy barrier of the rate-determining step (RDS) and\nenhancing the electrocatalytic performance. Furthermore, the urea\ndegradation rates of Pt<sub>NC</sub>/NiMn-MOF (96.1%) and NiMn-MOF\n(90.3%) are significantly higher than those of Ni-MOF and the most\nreported advanced catalysts. This work provides valuable insights\nfor designing catalysts applicable to urea-rich wastewater treatment\nand energy-saving hydrogen production.