Alkaline anion exchange membrane fuel cells (AEMFCs) are widely considered a vital direction for next-generation sustainable hydrogen energy conversion technologies due to their compatibility with non-precious-metal catalysts, low system costs, and high safety profile.

However, in alkaline media, the kinetics of the hydrogen oxidation reaction (HOR) are significantly sluggish. Especially under high-current-density operating conditions, limitations in proton-coupled transport at the electrode/electrolyte interface and an imbalance in the adsorption strength of reaction intermediates severely restrict overall fuel cell performance.

Ruthenium (Ru), a platinum group metal that is less expensive than platinum (Pt) yet shares a similar d-band electronic structure, is viewed as a promising alternative for developing low-cost, high-performance alkaline HOR catalysts. Nevertheless, its interfacial reaction kinetics and device performance still require breakthroughs.

To address these challenges, Researcher Zeng Lingyou and Professor Ding Shujiang from the School of Chemistry at Xi'an Jiaotong University (XJTU) have collaborated with Professor Guo Shaojun from Peking University to propose a catalyst design strategy based on "rare-earth single-atom modulation of built-in electric fields and interfacial water molecule orientation."

Through a controllable cation exchange and partial reduction process, the research team constructed a Gd (Gadolinium) single-atom-embedded Ru/RuOₓ heterostructure catalyst (Ru/RuOₓ-Gd@C).

This strategy utilizes isolated Gd atoms to induce a stronger asymmetric charge distribution at the Ru/RuOₓ interface, enhancing the heterostructure's built-in electric field, which in turn modulates the surface oxophilicity of Ru active sites and the orientation of interfacial water molecules.

The study demonstrates that electronic-structure tuning induced by Gd single atoms optimizes the coverage of hydroxyl species on the catalyst surface. This promotes the orientational reconstruction of the "oxygen-down" water molecule configuration (H2O↓) at the electrode/electrolyte interface.

The ordered water structure further strengthens the interfacial hydrogen-bonding network, thereby constructing highly efficient proton-conduction channels that significantly accelerate alkaline HOR kinetics.

Based on this mechanism, the Ru/RuOₓ-Gd@C catalyst achieved a mass activity of 8.87 mA μgRu^-1 (6.6 times higher than commercial Pt/C), and an exchange current density of 0.39 mA cm^-2 (2.0 times higher than commercial Pt/C).

The assembled anion exchange membrane fuel cell also achieved a Ru mass-normalized peak power density of 16.3 W mg_Ru^-1 and demonstrated stable operation for over 60 hours. This study elucidates the interfacial regulation mechanism underlying efficient alkaline HOR catalysis across three dimensions: built-in electric-field modulation, surface oxophilicity optimization, and water-molecule orientation reconstruction. It provides innovative ideas for developing alkaline hydrogen fuel cell anode catalysts with low noble-metal loading, high performance, and high stability.

The findings have been published in Angewandte Chemie International Edition, a top-tier international chemistry journal, under the title Interfacial Water Reorientation in Gadolinium-Doped Ru/RuOₓ Heterostructures Boosts Alkaline Hydrogen Oxidation Electrocatalysis.