PdPt Alloy Nanoframes with Rugged Surfaces: Efficient Bifunctional Fuel Cell Catalysts in a Broad pH Range

The catalytic performance of a catalyst is mainly determined by its surface structure, and superior catalytic activities have been observed on low-coordination surface sites. However, poor stability of low-coordination sites was observed during catalysis due to easier oxidation of these sites. By far, fabricating the catalysts with abundant low-coordination sites and stabilizing them still faces a significant challenge. Herein, we show the synthesis of an emerging type of PdPt alloy nanoframe wherein the ridges are composed of rugged surfaces with high-density, low-coordination sites. The synthesis of nanoframes mainly consists of two steps: preparation of PdPt alloy concave nanocubes and subsequent site-selective chemical etching. The nanoframe structure would endow low-coordination sites with excellent catalytic stability, preventing dissolution, migration, and aggregation of these active sites during catalysis. Electrochemical studies on the oxygen reduction reaction (ORR) catalysis show that it can deliver superior mass activities tens of times higher than that of commercial Pt/C catalysts in a broad pH range (from 1 to 13), with negligible activity decay after 40 000 cycles. In addition, as-prepared nanoframes can also exhibit excellent catalytic activity and stability toward methanol and ethanol oxidation reactions, with mass activities up to 19.55 and 28.96 A/mg Pd+Pt, respectively, which are 19 and 47 times that of commercial Pt/C catalysts. Theoretical calculations reveal that the coexistence of PdPt alloy components and high-density, low-coordination sites both is important for enhanced catalytic activities. This new strategy to stabilize the low-coordination sites on Pt-based electrocatalysts by constructing frame structures would shed new light on the rational design and synthesis of highly efficient electrocatalysts.