By Magnetic-Electric Field Induction of Ni─O─Fe Heterogeneous Oxygen Bridge Structure to Promote the Formation of *OH and to Enhance Urea Oxidation Reaction

Abstract

Regulating electronic structure via a uniform magnetic field effectively optimizes catalytic performance, yet rationally utilizing external magnetic fields to tune catalyst structure, promote small-molecule oxidation, and clarify mechanisms remains a key challenge. Here, a 0.7 T magnetic field was introduced during Fe-Ni₂P@NF electrochemical activation to construct a Ni─O─Fe heterogeneous oxygen bridge, boosting urea oxidation (UOR) and hydrogen evolution (HER). In situ Raman revealed the magnetic field-induced Ni─O─Fe formation on 0 T and 0.7 T Fe-Ni₂P@NF surfaces—this structure is more stable than NiOOH and functions as an electron transfer channel from Fe to Ni. Infrared spectroscopy revealed synergistic dual-site behavior: Ni sites enhance urea adsorption, while Fe sites in the Ni─O─Fe bridge stabilize *OH species; electron donation from Fe to Ni through the oxygen bridge promotes Ni²⁺ oxidation to higher-valent states (Ni³⁺/Ni⁴⁺), activating Ni centers for UOR. DFT calculations supported this electronic modulation mechanism—Fe-mediated electron transfer upshifts the Ni d-band center, strengthening urea adsorption and lowering the *NH─O→*N─O rate-determining step barrier. Notably, at 100 mA cm⁻², 0.7 T-Fe-Ni₂P@NF powers the HER//UOR electrolyze at only 1.54 V, outperforming water electrolyzes (1.62 V).