Expediting the Volmer Step of Alkaline Hydrogen Oxidation with High-Efficiency and CO-Tolerance by Ru–O–Eu Bridge

The quest for economical and highly efficient nanomaterials for the alkaline hydrogen oxidation reaction (HOR) is imperative in advancing the technology of anion exchange membrane fuel cells (AEMFCs). Efforts using Pt-based electrocatalysts for alkaline HOR are greatly plagued by their finitely intrinsic activities and significant CO poisoning, stemming from the difficulty of simultaneously optimizing surface adsorption toward different hydrogen-related adsorbates. Herein, Ru clusters coupled with Eu₂O₃ immobilized within N-doped carbon nanofibers (Ru/Eu₂O₃@N-CNFs) are developed toward drastically boosted electrocatalysis for HOR via a d-p-f gradient orbital coupling strategy. Theoretical calculations and in situ operando spectroscopy discover that the induction of Eu₂O₃ optimizes the Ru site electronic structure via constructing the gradient orbital coupling of Ru(3d)-O(2p)-Eu(4f), leading to optimal H intermediates, improved adsorption ability of OH and reduced energy barrier of water formation, and promoted CO oxidation, endowing the Ru/Eu₂O₃ as the promising catalyst alternative for fast alkaline hydrogen electrooxidation. As a result, the Ru/Eu₂O₃@N-CNFs reach an impressive kinetic current densities (j_k) value of 156.3 mA cm^-2 at 50 mV (38.4 times higher than Pt/C), and decent stability over 35000 s continuous operation. This comprehensive investigation featuring d-p-f gradient orbital coupling provides valuable insights for the strategic development of high-performance Ru-based materials for HOR and beyond.