Synthesis and X-ray Characterization of Cobalt Phosphide (Co₂P) Nanorods for the Oxygen Reduction Reaction

Abstract

Low temperature fuel cells are clean, effective alternative fuel conversion technology. Oxygen reduction reaction (ORR) at the fuel cell cathode has required Pt as the electrocatalyst for high activity and selectivity of the four-electron reaction pathway. Targeting a less expensive, earth abundant alternative, we have developed the synthesis of cobalt phosphide (Co2P) nanorods for ORR. Characterization techniques that include total X-ray scattering and extended X-ray absorption fine structure revealed a deviation of the nanorods from bulk crystal structure with a contraction along the b orthorhombic lattice parameter. The carbon supported nanorods have comparable activity but are remarkably more stable than conventional Pt catalysts for the oxygen reduction reaction in alkaline environments.

Molybdenum Polysulfide Chalcogels as High-Capacity, Anion-Redox-Driven Electrode Materials for Li-Ion Batteries

“…Collecting operando PDFs allows for tracking the evolution of the local structure for materials that lack long-range ordering, which is particularly useful for chalcogels. 48,[72][73][74][75][76][77] Here, PDFs of the MoS x electrode cycled at constant current of 0.61 (9) mA g −1 (≈ C/16) (Figure 8a) capture the Mo-S bonds centered at 2.45Å in Figure 8b, which is unchanged upon discharge to 600.5 mAh g Coulombic efficiency is maintained at 98.9% for the second and third cycles. One of the many strategies for increasing Li ion kinetics includes increasing the electrode surface area.…”

Advances in Transition‐Metal Phosphide Applications in Electrochemical Energy Storage and Catalysis

“…Similar activity for the ORR was confirmed for cobalt phosphide nanoparticles encased in boron and nitrogen codoped graphitic layers and monodispersed CoP nanorods/commercial carbon . They thought the electronic effect from the synergistic interactions between TMPs and the carbon material is of key importance to enhance the ORR performance.…”

Phase Diversity of Nickel Phosphides in Oxygen Reduction Catalysis

“…[50] Also transition metal phosphides (TMPs), formed by the combination of transition metal and phosphorous, have been proven to be highly active catalysts in different reactions, not only in strong acidic solution but also in strong alkaline and neutral media. [56,58] Previous works indicate that the crystalline phase structure of TMPs is a main factor to determine their catalytic activity. [51][52][53][54][55][56][57] More recently, a TMP with a combination of cobalt and phosphorous due to its high electrical conductivity and unique structural, physical, and chemical properties has also shown promising ORR activity in alkaline medium.…”

“…[59][60][61] It is reported that TMPs with high P content demonstrate high corrosion resistance in both alkaline and acidic solutions resulting from the thermodynamically enhanced stability of the metal in alloy formation with phosphorus. [61] Although TMPs have been used as high performance catalysts for several electrochemical reactions such as hydrogen evolution and oxygen evolution, [55][56][57][58][59][60] their ORR activity except a recent few study by cobalt phosphide remain untouched. On the other hand, metal-rich TMPs exhibit metallic character with high electrical conductivity, which is beneficial.…”

“…[61] However, increasing P content can greatly delimit the electron delocalization of the metal atoms, and thus hamper the conductivity, resulting in a lower catalytic activity. [58] Based on these research works, developing new TMP-based electrocatalyst materials for ORR will be appealing. [61] Therefore, balancing the transition metal and phosphorous ratio is a key factor to design TMP-based catalysts with high stability without seriously blemishing their conductivity, which in turn results in an increase in catalytic activity.…”