# Electrocatalytic and Magnetic Properties of Porous Iron Phosphide Nanorods

## TL;DR

Researchers developed a new, low-temperature method to make pure iron phosphide nanorods with useful magnetic and electrocatalytic properties.

## Contribution

A low-temperature, solution-based method to synthesize phase-pure FeP nanoparticles using cost-effective precursors.

## Key findings

- The synthesized FeP nanorods show paramagnetic behavior, unlike bulk FeP which is antiferromagnetic.
- The nanorods achieved an overpotential of 267 mV for hydrogen evolution in acidic media.
- The electrocatalytic activity remained stable for 12 hours at high current density.

## Abstract

Nanoscale transition
metal phosphide systems hold significant technological
potential due to their distinctive optoelectronic properties, high
catalytic activity, superparamagnetism, and high diffusion coefficient
of Na/Li ions. However, attempts to synthesize phase-pure FeP, a promising
electrocatalyst, have utilized expensive and/or highly reactive phosphide
precursors such as tri-n-octylphosphine (TOP), white
phosphorus (P4), tris­(trimethylsilyl)­phosphine (P­(TMS)3), and tri-n-butylphosphine. These methods
often require high temperatures and/or multistep reaction processes.
Here, to address these limitations, we present a solution-based synthesis
method to produce phase-pure FeP nanoparticles. In this synthesis,
we react iron oxyhydroxide (β-FeOOH) as a cost-effective, environmentally
friendly, and air-stable source of iron with tris-diethylaminophosphine
P­(NEt2)3 as a phosphorus source at 280 °C.
The resulting FeP is formed in a porous nanorod morphology. The particles
were characterized by TEM and XPS. Magnetic measurements of the phase-pure
FeP nanoparticles indicate paramagnetic behavior, contrasting the
antiferromagnetic behavior observed in bulk FeP. In addition to their
unique magnetic properties, these porous FeP nanorods demonstrate
promising HER performance, achieving an overpotential of 267 mV at
a geometric current density of −10 mA cm–2 in acidic media, with stable electrocatalytic activity maintained
for up to 12 h at −50 mA cm–2. This study
represents the first documented low-temperature, time-efficient, solution-based
thermal decomposition method for synthesizing phase-pure FeP nanoparticles,
using tris­(diethylamino)­phosphine P­(NEt2)3 and
iron oxyhydroxide (β-FeOOH) as sources of phosphorus and iron,
respectively, at 280 °C.