PtCl _x Intermediates Strategy to Ultrahigh-Loading Sub-3 nm Pt/C Catalysts for H₂-Air Fuel Cells

High-loading Pt/C catalysts are essential for reducingthe masstransfer impedance of the catalytic layer in H-2-air fuelcells. This work establishes an incipient wetness impregnation (IWI)-basedsynthesis method for preparing sub-3 nm Pt/C catalysts with a loadingup to 60 wt %. A two-step reduction strategy involving PtCl x /C intermediates (PtCl x /C-IMD) has been developed to overcome the limitations of the traditionalIWI method in controlling the size of Pt-NPs at ultrahighloadings. We found that (1) the formation of Pt-NPs fromPtCl( x )/C-IMD differs significantly fromthat of the simple H2PtCl6/C precursor, as PtCl x /C-IMD can be converted to Pt/C at an ultralowtemperature of 100 & DEG;C, which is 50 & DEG;C lower than H2PtCl6/C. (2) The size of Pt-NPs is primarilydetermined during the low-temperature formation stage rather thanduring high-temperature postsintering. Furthermore, a fuel cell manufacturerhas demonstrated that the as-prepared 60% Pt/C catalyst, when usedin a single H-2-air fuel cell, achieves a high power densityof 1.03 W/cm(2) at 0.65 V with a low Pt loading of 0.2 mg/cm(2), outperforming the state-of-the-art commercial 60% Pt/C.In other words, this work paves an efficient way for the productionof high-loading Pt/C catalysts for fuel cells.