N-Doped FeP₄ Nanoparticles on Carbon Cloth as Catalysts for Electrolytic Hydrogen Evolution

Theoretically, the stronger electronegativity of N compared to that of P suggests that N-doped FeP4 could reduce the adsorption energy of hydrogen, potentially enhancing the kinetics of the hydrogen evolution reaction (HER) and improving its electrochemical characteristics. Experimentally, a three-dimensional (3D) porous dodecahedron N-doped FeP4 nanoparticle array catalyst developed on carbon cloth (CC) was investigated. The synthesized N-doped FeP4/CC nanoparticle electrocatalysts demonstrated satisfactory HER performance. These electrocatalysts showed a current density (J) of 10 mA/cm–2 at an overvoltage of 87 mV in a 0.5 M H2SO4 solution, indicating that the electronically modified FeP4 (N-FeP4/CC) catalyst exhibited superior HER activity. Additionally, the overpotential for the N-doped FeP4/CC nanoparticle catalyst was 347 mV for HER in simulated seawater solution (0.5 M H2SO4 + 0.5 M NaCl), demonstrating the exceptional catalytic activity of the N-doped FeP4/CC nanoparticle catalyst. Density functional theory (DFT) calculations showed that N doping could synergistically improve the Gibbs free energy of hydrogen adsorption (ΔGH*) of FeP4 (−0.29 eV), which was lower than that of undoped FeP4 (0.41 eV). This supports the theoretical proposition that modifying the electronic structure can enhance the electrolysis hydrodynamics and catalytic performance, aligning with experimental findings. This study may provide a strategy for optimizing the electronic structure of seawater splitting.