Encapsulating Nickel‐Iron Alloy Nanoparticles in a Polysilazane‐Derived Microporous Si−C−O−N‐Based Support to Stimulate Superior OER Activity

Abstract

The in situ confinement of nickel (Ni)‐iron (Fe) nanoparticles (NPs) in a polymer‐derived micro‐/mesoporous silicon carboxynitride (Si‐C‐O‐N)‐based support is investigated to stimulate superior oxygen evolution reaction (OER) activity in an alkaline media. Firstly, we consider a commercial polysilazane (PSZ) and Ni and Fe salts to be mixed together in N,N‐dimethylformamide (DMF) in order to prepare a series of Ni‐Fe:organosilicon coordination complexes. The latter are then heat‐treated at 500 °C in flowing argon to form the title compounds. By considering a Ni:Fe ratio of 1.5, face centred cubic (fcc) NixFey alloy NPs with a size of 15‐30 nm are in situ generated in a micro‐/mesoporous Si‐C‐O‐N‐based support displaying a specific surface area (SSA) as high as 237 m2⋅g‐1. Hence, NPs are renderedaccessible to promote electrocatalytic water oxidation. An OER overpotential as low as 315 mV at 10 mA⋅cm‐2 is measured. This high catalytic performance (considering that the metal mass loading is as low as 0.24 mg cm−2) is rather stable as observed after an activation step; thus, validating our synthesis approach and opening further investigations. This is clearly attributed to both the strong NP‐matrix interaction and the confinement effect of the matrix as highlighted through post mortem microscopy observations.