Recently, Dr. Huiqi Li, Assistant Professor at the College of Chemistry and Environmental Engineering of Shenzhen University, in collaboration with the group of Prof. Héctor D. Abruña at Cornell University, achieved an important breakthrough in the design of electrocatalysts for anion-exchange membrane fuel cells (AEMFCs). The work, titled “Rational design of high-performance low-loading oxygen reduction catalysts for alkaline fuel cells,” was published in Nature Materials. Dr. Li is the first author of the article.
Hydrogen fuel cells represent a key pathway toward zero-carbon energy. Among them, AEMFCs have attracted growing attention because their alkaline operating environment enables the use of a wider range of catalyst materials, including low-cost and earth-abundant options. However, the sluggish kinetics of the oxygen reduction reaction (ORR) continues to be a major barrier to the large-scale deployment of AEMFCs. More critically, fundamental understanding of the ORR mechanism has been largely established in acidic media and often fails to translate into alkaline conditions.
In acidic media, a widely used descriptor for ORR activity is the adsorption energy of oxygen or hydroxyl intermediates (*O or *OH). According to the Sabatier principle, an intermediate adsorption strength leads to optimal performance, forming the basis of the classic “volcano plot” used to guide the design of Pt-based ORR catalysts. Because Pt binds oxygen slightly too strongly in acid, weakening this binding has proven effective for enhancing activity.
However, this volcano relationship does not hold in alkaline media. A representative example is palladium: although Pd shows lower activity than Pt in acid due to overly strong oxygen binding, it exhibits higher activity than Pt in alkaline electrolytes. This striking reversal highlights the critical influence of electrolyte pH on ORR kinetics and calls for a reassessment of catalyst design principles. Despite numerous attempts, there is still no consensus regarding the key factors governing alkaline ORR activity on metal surfaces.
To address this challenge, Dr. Li and co-workers proposed a modified volcano plot tailored for alkaline media by incorporating two essential factors: the coverage of adsorbed hydroxyl species (Θ*OH) and the interfacial electric field. This modified volcano plot predicts that introducing tensile strain into Pt enhances its ORR activity in alkaline media—a trend opposite to that observed in acid. Guided by this concept, the team designed a sandwich-like PdHx@Pt nanosheet (NS) catalyst, in which ultrathin Pt nanosheets with exposed {111} facets grow epitaxially on PdHx nanosheets, generating expansive strain and simultaneously improving the oxidative stability of Pd.
The PdHx@Pt NS catalyst exhibits outstanding activity in alkaline electrolytes, delivering a 49-fold increase in mass activity compared to commercial Pt/C. In fuel cell testing, the catalyst enabled a peak power density (PPD) of 1.67 W cm-2 with a loading of 10 µgPGM Cathodecm-2. Further optimization delivered a PPD of 21.7 W mg-1PGM Cathode+Anode with a total specific catalyst cost US$ 1.27 kW-1, surpassing the US Department of Energy’s platinum group metal loading and cost targets. This study provides valuable insights into catalyst design for the alkaline ORR.
Link to paper: https://www.nature.com/articles/s41563-025-02422-4
College of Chemistry and Environmental Engineering