Three-step method with self-sacrificial Co to prepare a uniform 5 nm-scale Pt catalyst for the oxygen reduction reaction

Abstract

The catalytic activity of Pt-based catalysts for fuel cells is largely determined by the particle size and the dispersion of Pt. Normally, the electrodeposition of Pt cannot avoid a large particle size and agglomeration. For ensuring uniformity and a small size in the 5 nm scale of Pt, a three-step method was creatively applied to deposit Co first on defective mesoporous carbon (CMK-3-D) as a self-sacrificial template and as anchor points for Pt deposition. Second, we immersed Co/CMK-3-D in a mixed Pt and acid solution. Finally, the further growth of Pt was controlled by pulse reverse electrodeposition. Due to the trapping effect of defect holes from CMK-3-D, there was a small amount of nano-Co left in the catalyst carrier. The catalyst was finally composed of nano-Co and Pt nanoparticles (CoPt/CMK-3-D). The residual Co provided a large number of active sites, which promoted the excellent activity and stability of Pt due to a synergistic effect. Compared with commercial Pt/C, the specific activity of the catalyst was increased by about 2.3 times. After a 10 000 cycles test, the half-wave potential loss was only 6.4 mV. The high catalytic property of CoPt/CMK-3-D was attributed to its excellent dispersibility, small size, and the synergistic effect of the carrier and Co with Pt.