Manganese-tuned chemical etching of a platinum–copper nanocatalyst with platinum-rich surfaces

• PtCu particles with Pt-rich surfaces were used as precursors for etching.
• Manganese-tuned etching induced the formation of abundant Pt active sites.
• MOR activity of MnA-PtCu/C was ca. 4.0 times higher than that of Pt/C.
• Catalytic durability of MnA-PtCu/C towards MOR was improved significantly.

This work presents a modified chemical etching strategy to fabricate binary metal nanocatalysts with large active areas. The strategy employs PtCu alloy particles with Pt-rich outer layers as the precursor and manganese species to manipulate the acid leaching processes. X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy techniques are used to analyze the catalyst structures and the tuning mechanism of manganese species during etching. It is found that the introduction of manganese species allows more Pt active sites to be formed onto the catalyst surface after etching, possibly due to reduction in the number of Pt atoms enclosed inside particles. The electrochemically active surface area of the synthetic MnA-PtCu/C catalyst increases by 90% relative to commercial Pt/C catalyst. As a result of the increase in active areas and the additional promotion effects by Cu, the MnA-PtCu/C catalyst reveals a methanol oxidation activity 1.7 and 4.0 times higher than that of the synthetic PtCu/C and commercial Pt/C catalysts, respectively.