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 FeP 4 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 FeP 4 nanoparticle array catalyst developed on carbon cloth (CC) was investigated. The synthesized N-doped FeP 4 /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 H 2 SO 4 solution, indicating that the electronically modified FeP 4 (N-FeP 4 /CC) catalyst exhibited superior HER activity. Additionally, the overpotential for the N-doped FeP 4 /CC nanoparticle catalyst was 347 mV for HER in simulated seawater solution (0.5 M H 2 SO 4 + 0.5 M NaCl), demonstrating the exceptional catalytic activity of the N-doped FeP 4 /CC nanoparticle catalyst. Density functional theory (DFT) calculations showed that N doping could synergistically improve the Gibbs free energy of hydrogen adsorption (ΔGH*) of FeP 4 (−0.29 eV), which was lower than that of undoped FeP 4 (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.