Oxygen Reduction on Small Supported Platinum Particles

A series of four catalysts with 5, 10, 20, and 30 weight percent of Pt on carbon has been prepared and incorporated into Teflon‐bonded electrodes. The mean Pt crystallite sizes, as determined by chemisorption, were less than 1, 1.1, 1.4, and 4.1 nm. Also, a Teflon‐bonded Pt‐black electrocatalyst with a Pt crystallite size of 12 nm was prepared. These electrodes were used for the cathodic reduction of dioxygen in at 298 K. The turnover frequency decreased by a factor of 20 with decreasing particle size. Since surface area per weight of metal increases as particle size decreases, the optimum Pt crystallite diameter is about 3 nm.