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 reducing the mass transfer impedance of the catalytic layer in H 2 -air fuel cells. This work establishes an incipient wetness impregnation (IWI)-based synthesis method for preparing sub-3 nm Pt/C catalysts with a loading up 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 traditional IWI method in controlling the size of Pt NPs at ultrahigh loadings. We found that (1) the formation of Pt NPs from PtCl x /C-IMD differs significantly from that of the simple H 2 PtCl 6 /C precursor, as PtCl x /C-IMD can be converted to Pt/C at an ultralow temperature of 100 °C, which is 50 °C lower than H 2 PtCl 6 /C. (2) The size of Pt NPs is primarily determined during the low-temperature formation stage rather than during high-temperature postsintering. Furthermore, a fuel cell manufacturer has demonstrated that the as-prepared 60% Pt/C catalyst, when used in a single H 2 -air fuel cell, achieves a high power density of 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 production of high-loading Pt/C catalysts for fuel cells.