Hollow FeP/FeO Hybrid Nanoparticles on Carbon Nanotubes as Efficient Electrocatalysts for the Oxygen Evolution Reaction.

We develop a method to prepare hollow FeP/FeO hybrid nanoparticles supported on carbon nanotubes (CNTs), which could be used as highly active and efficient electrocatalysts. The Fe@FeO/CNT hybrids were first synthesized by annealing the CNTs adsorbed with Fe(NO), followed by controlled phosphorization treatment. They exhibit an outstanding catalytic activity for oxygen evolution reaction (OER) with a low overpotential of 229 mV at a current density of 10 mA cm, a high turnover frequency value of 0.35 s at an overpotential of 300 mV, and an ultralow Tafel slope of 27.6 mV dec, which is much better than that of FeP/FeO, FeP/CNTs, FeO/CNTs, and the commercial RuO electrocatalyst. More importantly, the Tafel slope is much lower than most non-noble metal-based OER electrocatalysts reported in the previous literature studies as far as we know. The excellent OER performance benefits from the electron transfer from FeO to FeP confirmed by X-ray photoelectron spectroscopy, together with good conductivity of CNTs. This hybrid structure supported on conductive CNTs may offer an efficient method to design earth-abundant and low-cost electrocatalysts for OER in practical applications.