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

The electro-oxidation of H2 (HOR) is 200× 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) 1.6× larger than Pt. However, PtSb2@Pt exhibited a higher HBE, lowering the jo value by 1.2× compared to Pt. This work demonstrated that high alkaline HOR activity can be achieved solely by tuning the HBE.