Ir-oxide mediated surface restructure and corresponding impacts on durability of bimetallic NiO_x@Pd nanocatalysts in oxygen reduction reaction

With proper conjunctions between inter/intra-particle domains, the activity and durability of heterogeneous nanocatalysts (NCs) can be substantially improved by more than an order. In this study, tri-metallic NCs comprising an Ir-clusters decorated unconformable Pd-shell over amorphous NiOx core crystal underneath (namely NPI) are developed for oxygen reduction reaction (ORR) in alkaline medium (0.1 M KOH). Results for NPI NCs with different extents of Ir decoration (1 and 14 wt%) are compared for clarifying the configuration effects corresponding to ORR performance. For the optimum case with an Ir loading of ∼1.0 wt%, the mass activity (MA) is 2066.8 mAmg⁻¹. This value is ∼31-folds increased as compared to that of commercial J.M.-Pt/C catalyst (20 wt% Pt) at 0.85 V vs RHE (67.1 mA mg⁻¹). Moreover, as prepared NPI-0025 NC exhibits nearly 100% stability when operated up to 21 k accelerated degradation test (ADT) cycles. By cross-referencing results of physical structure inspections and electrochemical analysis, we reveal that such a high ORR performance could be attributed to the incorporation of Ir atoms in defect sites of Ni–Pd interfaces. These Ir atoms facilitate the O₂ splitting by electronegativity differences to the adjacent sites, therefore, improves the ORR performance of NPI NCs.