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

The in situ confinement of nickel (Ni)‐iron (Fe) nanoparticles (NPs) in a polymer‐derived microporous 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 chlorides to be mixed in N,N‐dimethylformamide (DMF) and deliver after overnight solvent reflux a series of Ni−Fe : organosilicon coordination polymers. 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 porous Si−C−O−N‐based matrix displaying a specific surface area (SSA) as high as 237 m2 ⋅ g−1. Hence, encapsulated NPs are rendered accessible 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. 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. We diverge from conventional methods consisting to deposit catalyst nanoparticles onto a porous support and move toward an in situ chemical approach to form high surface area ceramic‐based supports containing p block elements (Si, C, O, N) and encapsulating face‐centered cubic NixFey nanoparticles with boosted OER catalytic activity and stability.