PtM (M = Fe, Co, Ni) Bimetallic Nanoclusters as Active, Methanol-Tolerant, and Stable Catalysts toward the Oxygen Reduction Reaction

Tailoring PtM (M = Fe, Co, Ni) bimetallic electrocatalysts into nanoclusters (NCs) without any protective agents with diameters of about 2–5 nm is considered as an effective strategy to improve electrochemical performance, reduce the mass loading of precious Pt, and enhance methanol tolerance in the oxygen reduction reaction (ORR). However, how to synthesize bimetallic NCs with relatively controllable size and how to anchor and disperse PtM (M = Fe, Co, Ni) bimetallic NCs onto a suitable matrix are key issues to guarantee durable catalytic performance and stability of bimetallic NCs because NCs possess high surface energy, and it is easy for them to aggregate. Hence, in this paper, we demonstrated a low-temperature impregnation–reduction method to fabricate PtM (M = Fe, Co, Ni) bimetallic NCs without any protective agents immobilized on XC-72 carbon with a 10 wt % PtM loading, which exhibited more satisfactory ORR performance. In particular, PtNi/C presented the best ORR catalytic activity among the three catalysts and commercial Pt/C (20 wt % Pt loading) due to the synergistic effects of the unique electronic structure, smaller particle size, and stable adhesion with substrate. Electrochemical characterization indicated that a maximal catalytic activity was achieved at a Pt:Ni atomic ratio 0.8:0.2, and the mass activity (MA) was about 2.74 times greater than that of Pt/C. Furthermore, the Pt0.8Ni0.2/C catalyst possessed notable methanol tolerance and stability, which is vital for practical applications. As a result, this facile and effective synthesis strategy opens up new horizons to promote direct methanol fuel cells (DMFCs) into practical applications.