This work presents simple post-treatment methods to selectively and partially remove the Pd core of Pd–Pt core–shell (Pt@Pd/C) catalysts. The proton exchange membrane fuel cell with the post-treated Pt@Pd/C cathode (Pt loading: 0.10 mg∙cm⁻²) delivers an impressive peak power density of 1.2 W∙cm⁻². The partial removal of Pd core endows an ultrahigh oxygen reduction reaction (ORR) mass activity of 0.32 A∙mg_PGM⁻¹ when normalized to the platinum group metal (PGM) mass, or equivalently 0.55 A∙mg_Pt⁻¹ at 0.9 V measured in a fuel cell. The post-treatment thickens the Pt shells and mitigates the Pd dissolution during potential cycling. As a result, the post-treated core–shell catalyst demonstrates superior durability in ORR mass activity and polarization power density retention than untreated core–shell catalyst and benchmark Pt/C. In-situ inductively coupled plasma-mass spectrometry (ICP-MS) results highlight that the amount of dissolved Pd in post-treated core–shell catalyst is 17-times lower than that of the untreated one. Our findings highlight the importance of structural tuning of catalysts in enhancing their mass activity and durability.

As a promising fuel candidate, ammonia has been successfully used as anode feed in alkaline fuel cells. However, current technology in catalysts for ammonia electro-oxidation reaction (AOR) with respect to both cost and performance is inadequate to ensure large scale commercial application of direct ammonia fuel cells. Recent studies found that alloying Pt with different transition metals and controlling the morphology of catalysts can improve the AOR activity, and thus potentially can solve the cost issue. Herein, (100)-terminated Pt-M nanocubes (M = 3d-transition metals Fe, Co, Ni, Zn) are synthesized via wet-chemistry method and their catalytic activities toward AOR are evaluated. The addition of Fe, Co, Ni and Zn elements can enhance the AOR activity due to decrease in oxophilicity of platinum and bifunctional mechanism. Pt-Zn exhibits the maximum mass activity and specific activity with values of 0.41 A/mg_Pt and 1.69 mA/cm² that are 1.6 and 1.8 times higher than Pt nanocubes, respectively. Pt-Fe, Pt-Co and Pt-Ni nanocubes also illustrate higher mass and specific activities compared to Pt nanocubes.

L1₀-FePt nanoparticles (NPs) with high chemical ordering represent effective electrocatalysts to reduce the cost and enhance their catalytic performance in fuel cells. A molecular strategy of preparing highly ordered FePt NPs was used by direct pyrolysis of a Fe, Pt-containing bimetallic complex. The resultant L1₀-FePt NPs had very high crystallinity as reflected by the obvious diffraction patterns, clear lattice fringes and characteristic X-ray diffraction peaks, etc. Besides, the strong ferromagnetism with room temperature coercivity of 27 kOe further confirmed the face-centered tetragonal (fct) phase in good agreement with the ordered nanostructures. The FePt NPs can be used as electrocatalysts to catalyze oxygen reduction reaction (ORR) in an O₂-saturated 0.1 M HClO₄ solution and hydrogen evolution reaction (HER) in the 0.5 M H₂SO₄ electrolyte with much better performance than commercial Pt/C, and showed quite high stability after 10, 000 cycles. The strategy utilizing organometallic precursors to prepare metal alloy NPs was demonstrated to be a reliable approach for improving the catalytic efficiency in fuel cells.