Boosting the Catalytic Performance of Iron Phosphide Nanorods for the Oxygen Evolution Reaction by Incorporation of Manganese

The lack of efficient and stable oxygen evolution reaction (OER) catalysts comprising inexpensive Earth-abundant materials limits the viability of water splitting as a clean and renewable source of energy. In this work, we report the synthesis of homogeneous ternary Fe_2–<i>x</i>Mn_<i>x</i>P nanorods with control of Mn incorporation (0 ≤ <i>x</i> ≤ 0.9) from the solution-phase reaction of manganese and iron carbonyl complexes with trioctylphosphine. The OER activity of Fe_2–<i>x</i>Mn_<i>x</i>P nanorods dramatically increases with the incorporation of Mn (overpotential as low as 0.44 V at 10 mA/cm² for <i>x</i> = 0.9), and the overpotential can be further decreased (by nearly 0.1 V) by postdeposition annealing. The enhanced OER activity and stability, along with the abundance and availability of Fe and Mn, make bimetallic manganese–iron phosphides a promising class of materials for more cost-effective and efficient water oxidation catalysis

Control of Composition and Size in Discrete Co_<i>x</i>Fe_2–<i>x</i>P Nanoparticles: Consequences for Magnetic Properties

In this work, a solution-phase method was developed for the synthesis of Co_<i>x</i>Fe_2–<i>x</i>P nanoparticles over all <i>x</i> (0 ≤ <i>x</i> ≤ 2). The nanoparticles vary in size, ranging from 17 to 20 nm in diameter with standard deviations ≤ 14%. The synthesis involves preparation of Co_<i>x</i>Fe_1–<i>x</i> alloy nanoparticles and high temperature conversion into crystalline ternary phosphide nanocrystals. The target composition can be controlled by the initial metal precursor ratio, and the size of Co_<i>x</i>Fe_2–<i>x</i>P (from 12 to 22 nm) can be tuned by varying the oleylamine/metal ratio. Mössbauer data show that Fe has a strong preference for the square pyramidal site over the tetrahedral site. Magnetic measurements on Co_<i>x</i>Fe_2–<i>x</i>P nanoparticles showed a strong compositional dependence of the Curie temperature (<i>T</i>_C); CoFeP and Co_0.7Fe_0.3P have <i>T</i>_C’s > 340 K and are superparamagnetic at room temperature