Controlling surface composition of bimetallic catalysts is of significance in energy conversion and storage. We synthesized a series of bimetallic catalysts of different surface composition on porous graphitic carbon (PtBi/PC, Pt₃Ni/PC, Pt₃Co/PC: figures A, C, E, G) with average diameter < 4 nm by controlled thermal treatment method.

Formic acid oxidation on Pt/C is performed via the poisoning path (figure B), whereas oxidation of formic acid to form CO₂ is done via the non-poisoning path on the PtBi/PC (figure D). The value of the peak current density is 4.6 times of that of the Pt/C catalysts. Pt₃Ni catalyst with Pt-skin surface showed over 300% increase in mass activity compared with Pt/C for the oxygen reduction reaction (figure F). When we tuned the surface composition to Ni-rich, it showed 300% increasein mass activity when compared with Pt/C towards oxidizing of HCOOH. Ethanol oxidation on Pt₃Co/PC with Pt-skin surface showed 2.5 times on mass activity than that of Pt/C. In addition, we proposed a new method to characterize Pt-skin or M-rich structure by using formic acid oxidation as probe reaction with the characterization of cyclic voltammetry and electrochemical in situFTIRs.

Our approach to control surface composition can be used to design nanocatalysts for different reaction and enhance their catalytic performances. and The method is simple and clean that is effective and promotional to be industrialized.