Pt-Co truncated octahedral nanocrystals: a class of highly active and durable catalysts toward oxygen reduction.

We report a facile and scalable synthesis of Pt−Co truncated octahedral nanocrystals (TONs) by employing Co(acac)2 as a precursor, together with CO molecules and Mn atoms derived from the decomposition of Mn2(CO)10 as a reductant and a {111} facet-directing agent, respectively. Both the composition and yield of the Pt−Co TONs could be varied through the introduction of CHCl3. When tested at 80 oC using membrane electrode assembly (MEA), the 4-nm Pt2.6Co TONs gave a mass activity of 294 A gPt-1 at beginning-of-life (BOL) and it increased to 384 A gPt-1 during recovery cycles. The mass activity at BOL only dropped by 24% after 30,000 voltage cycles at end-of-life (EOL) in a metal dissolution accelerated stress test. The Pt2.6Co/C catalyst outperformed the commercial TKK Pt3Co/C (230 A gPt-1 at BOL and 40% loss after 30,000 cycles at EOL) in terms of both activity and durability. Our systematic analysis suggested that the enhancement in activity can be attributed to a combination of small, uniform size and well-defined {111} facets. This new catalyst holds promise for applications in proton-exchange membrane fuel cells.