4.6 Article

Improved Alkaline Hydrogen Oxidation on Strain-Modulated Pt Overlayers at Ordered Intermetallic Pt-Sb Cores

Journal

ACS ENERGY LETTERS
Volume 8, Issue 1, Pages 685-690

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acsenergylett.2c02473

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The electro-oxidation of H2 in base is much slower than that in acid, which hinders the deployment of alkaline fuel cells. It is unclear whether the improved hydrogen oxidation reaction (HOR) performance of alloy materials is primarily due to hydrogen binding energy (HBE) or bifunctional effects. This study used ordered intermetallic compounds to produce strain-modulated Pt shells, and demonstrated that tuning the HBE can achieve high alkaline HOR activity independently from the bifunctional effect.
The electro-oxidation of H2 (HOR) is 200x slower in base than in acid, hampering the deployment of alkaline fuel cells. It is disputed whether the hydrogen binding energy (HBE) or a bifunctional effect is the primary contributor to the improved HOR performance of alloy materials, because these effects are difficult to disentangle. Here, we used ordered intermetallic compounds (OICs) to produce strain-modulated Pt shells, in which PtSb@Pt and PtSb2@Pt exhibited compressive or tensile strain, respectively, to Pt. The HBE was tuned by the crystal structure of the OICs, allowing us to use the same two elements in the alloy and thus remove convolution from the bifunctional effect. PtSb@Pt exhibited a weaker HBE than Pt, achieving an exchange current density (jo) 1.6x larger than Pt. However, PtSb2@Pt exhibited a higher HBE, lowering the jo value by 1.2x compared to Pt. This work demonstrated that high alkaline HOR activity can be achieved solely by tuning the HBE.

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