Oxophilic Sites Activate Asymmetric IrNi Atomic Dimers and Clusters for Efficient Hydrogen Oxidation and CO Tolerance
Multi-site coupling is a promising strategy for developing highly efficient and CO-resistant hydrogen oxidation reaction (HOR) catalysts for proton exchange membrane fuel cells (PEMFCs). However, designing multifunctional synergistic schemes for single-atom sites remains a significant challenge. Herein, we propose a dual-template-confined oxophilic engineering strategy to construct well-dispersed iridium-nickel (IrNi) atomic dimers adjacent to IrNi nanoclusters on porous nitrogen-doped carbon (IrNi Dimer/NC1.8-PNC). The paired IrNi dimer features an asymmetric Ir-N3 configuration coordinated with heteroatomic Ni-N3O via an N-bridge. Remarkably, IrNi Dimer/NC1.8-PNC exhibits a ~23-fold enhancement in mass activity (4.36 A mg−1 Ir at 20 mV) and 5-fold longer stability compared to benchmarking Pt/C toward HOR, while achieving a high rated power density of 1.18 W cm−2 in PEMFC anode applications. Furthermore, IrNi Dimer/NC1.8-PNC demonstrates superior CO tolerance over monometallic Ir and Pt/C in both half-cell and full-cell devices. Combined experimental and density functional theory studies reveal that oxophilic Ni modulates the electronic environment of Ir through alloying and dimer interactions, thereby enhancing HOR activity. Importantly, the asymmetric IrNi dimer enables efficient CO* and OH* co-adsorption while facilitating CO2* desorption, synergistically mitigating CO poisoning and improving atom utilization efficiency. This work provides a design strategy and fundamental insights for multi-site synergistic catalysts in PEMFC anodes.