Ordered PtCoFe Ternary Alloy Electrocatalyst Derived from Pre-Synthesized CoFe Hydroxide for Oxygen Reduction Reaction

The PtCo/C catalyst has been successfully applied to fuel cell driven vehicles due to its high catalytic activity and stability toward the oxygen reduction reaction (ORR). Introduction of Fe into the PtCo/C electrocatalyst probably can further improve the catalytic activity and reduce the catalyst cost. Here, an ordered PtCoFe ternary alloy electrocatalyst was prepared by deposition of Pt oxides on pre-synthesized CoFe hydroxide via the hydrothe rmal process, followed by treating ternary PtCoFe oxides in H-2/Ar flow at elevated temperatures. When H2PtCl6 is added into the CoFe hydroxides slurry, due to the presence of Co and Fe with partly positive charge, PtCl62- ions prefer to adsorb on Co and Fe atoms; then, Pt, Co, and Fe intimately contact and conveniently form an ordered ternary alloy during the following process. The X-ray diffraction patterns show superlattice peaks at 23.92 and 33.30 degrees, corresponding to the (001) and (110) facets of the ordered face-centered tetragonal alloy, which confirms the successful synthesis of the ordered Pt3Co2Fe/C alloy catalyst. The catalyst exhibits a mass activity of 0.24 A mgPt(-1) at 0.90 V vs the reversible hydrogen electrode, which is more excellent than the corresponding 0.12 A mgPt(-1) of PtCo/C and 0.09 A mgPt(-1) of the commercial 20 wt % Pt/C catalyst (Tanaka). Moreover, after 30,000 cycles, between 0.6 and 1.0 V at a scan rate of 100 mV s(-1), Pt3Co2Fe/C and Pt/C (TKK) catalysts exhibit 12 and 38 mV shifts of the half-wave potential, 14.9 and 56.5% decreases of the electrochemical active surface area, 17.9 and 50.4% loss of mass activity, and 3.99 and 3.86 electron transfer numbers, respectively. These results indicate that the Pt3Co2Fe/C electrocatalyst possesses much better catalytic activity and cycle stability than the commercial Pt/C catalyst, due to the lattice shrinkage, electronic structure, and ordered alloy caused by the introduced Co and Fe atoms. This work can provide an effective strategy for facile mass production of high-performance ternary electrocatalysts.