Effects of Catalyst Phase on the Hydrogen Evolution Reaction of Water Splitting: Preparation of Phase-Pure Films of FeP, Fe₂P, and Fe₃P and Their Relative Catalytic Activities

Abstract

The comparative catalytic activities of iron phosphides, Fe x P (x = 1-3), have been established with phase-pure material grown by Chemical Vapor Deposition (CVD) from single-source organometallic precursors. This is the first report of the preparation of phase-pure thin films of FeP and Fe 2 P and their identity was established with scanning-electron microscopy, X-ray photoelectron spectroscopy, and powder X-ray diffraction. All materials were deposited on fluorine-doped tin oxide (FTO) for evaluation of their activities towards the hydrogen evolution reaction (HER) of water splitting in 0.5 M H 2 SO 4. HER activity follows the trend Fe 3 P > Fe 2 P > FeP, with Fe 3 P having the lowest overpotential of 49 mV at a current density of 10 mA cm-2. Density functional theory (DFT) calculations are congruent with the observed activity trend with hydrogen binding favoring the iron-rich terminating surfaces of Fe 3 P and Fe 2 P over the iron-poor terminating surfaces of FeP. The results present a clear trend of activity with iron-rich phosphide phases outperforming phosphorus rich phases for hydrogen evolution. The films of Fe 2 P were grown using Fe(CO) 4 PH 3 (1), while the films of FeP were prepared using either Fe(CO) 4 P t BuH 2 (2) or the new molecule {Fe(CO) 4 P(H) t Bu} 2 (3) on quartz and FTO. Compound 3 was prepared from the reaction of PCl 2 t Bu with a mixture of Na[HFe(CO) 4 ] and Na 2 [Fe(CO) 4 ] and characterized by single-crystal X-Ray diffraction, ESI-MS, elemental analysis, and 31 P/ 1 H NMR spectroscopies. Films of Fe 3 P were prepared as previously described from H 2 Fe 3 (CO) 9 P t Bu (4).

Multifunctional Transition Metal‐Based Phosphides in Energy‐Related Electrocatalysis

“…Meanwhile, the computational simulation of HER process revealed that hydrogen tends to be stable at the bridging sites of Mo instead of P sites, thus engendering an ideal hydrogen adsorption Gibbs‐free energy on Mo 3 P (110) surface (Figure i). Besides, Schipper et al also observed a similar phenomenon in various stoichiometric ratios Fe‐based phosphides thin films . In their work, the HER activities followed the trend Fe 3 P>Fe 2 P>FeP because metal‐rich phosphides (Fe 3 P and Fe 2 P) surface had higher hydrogen coverages under thermoneutral hydrogen absorption conditions.…”

Self‐Supportive Mesoporous Ni/Co/Fe Phosphosulfide Nanorods Derived from Novel Hydrothermal Electrodeposition as a Highly Efficient Electrocatalyst for Overall Water Splitting

“…The peak at 707.2 eV is assigned to FeP specie, which is in agreement with the XRD pattern (Fe 2 P). Another peak at 715.7 eV is FeO specie due to the surface oxidation upon the exposure to air . Figure e (P 2p) shows three peaks at 127.9, 129.8, and 134.8 eV which are indexed to FeP (2p 3/2 ), FeP (2p 1/2 ), and FePO species, respectively .…”

Magnetocaloric materials: From micro- to nanoscale

“…The same motivation led Schipper and coworkers to grow FeP, Fe 2 P, and Fe 3 P thin films recently. 104 The films were grown by metal-organic chemical vapor deposition using single-source molecular precursors (Fe(CO) 4 PH 3 ) on fluorine-doped tin oxide to evaluate the system performance in hydrogen evolution. Both the experimental and the density functional theory calculations results show a higher hydrogen coverage for Fe-rich nanoparticles in comparison with P-rich.…”