Amorphous Ni_0.75Fe_0.25(OH)₂-Decorated Layered Double Perovskite Pr_0.5Ba_0.5CoO_3-δ for Highly Efficient and Stable Water Oxidation

Highly active, durable, and cost-effective electrocatalysts for water oxidation into oxygen gas hold a key role to realise a range of renewable energy solutions which include water-splitting and rechargeable metal-air batteries. Despite its very stable oxygen evolution reaction (OER) performance over large number of cycles, layered double perovskite PrBaCo₂O_5+δ (PBC) has a rather limited surface area. It is, thus, desirable to have the stability of PBC combined with the higher OER activity obtained by enlarging its surface area. Here, we used micro-sized PBC particles as the substrate for the deposition of nano-sized nickel-iron hydroxide, Ni_0.75Fe_0.25(OH)₂, which led to an order of magnitude improvement in the OER current density at 1.63 V versus the reversible hydrogen electrode for the amorphous Ni_0.75Fe_0.25(OH)₂-decorated PBC catalyst (A-Ni_0.75Fe_0.25(OH)₂+PBC), relative to the PBC catalyst. We showed that the crystal ordering of the decoration affects the OER activity, that is, the amorphous decoration provided a higher OER activity than the crystalline decoration by enabling a larger contact area between the catalyst and the aqueous electrolyte. The results we show here could potentially stimulate more innovative future works utilising simple chemical preparation route to realise high-performance hybrid OER catalysts involving novel constituents.