Activity Origin and Multifunctionality of Pt-Based Intermetallic Nanostructures for Efficient Electrocatalysis

Abstract

Pt-based intermetallic nanostructures have demonstrated higher electrocatalytic performances compared to random alloy structures. However, the origin of their enhanced catalytic properties remains elusive. Furthermore, a robust synthetic strategy for well-defined intermetallic nanostructures represents a challenge. Here, we reveal by combining theoretical and experimental results that the activity enhancement in intermetallic structures for the oxygen reduction reaction (ORR) originates from an intensified ligand effect. We prepared well-defined model nanocatalysts via confined nanospace-directed synthesis using mesoporous silica templates, which allows precise control over the size and shape of nanostructures. Importantly, this method can transform disordered alloy nanostructures into intermetallic analogues without agglomeration, enabling decoupling of an atomic ordering effect in catalysis. The prepared ordered intermetallic Pt3Co nanowires (O-Pt3Co NWs) can benefit from an intensified ligand effect, Pt-skin layer, and agglomeration-tolerant contiguous structure, which led to their enhanced ORR activity and durability compared to disordered alloy Pt3Co nanowires (D-Pt3Co NWs) and Pt/C catalysts. The multifunctionality of O-Pt3Co NWs is demonstrated with their higher activity and durability in the alkaline hydrogen evolution reaction and acidic methanol oxidation reaction than those of D-Pt3Co NWs and Pt/C catalysts. Furthermore, a proton exchange membrane fuel cell cathode based on O-Pt3Co NWs shows much better durability than a Pt/C-based one.

Pt‐based Intermetallic Nanocatalysts for Promoting the Oxygen Reduction Reaction

“…Reproduced from Ref. 31 with permission from the American Chemical Society (ACS).…”

“…The use of Pt–M intermetallic catalysts can drive further promotion in catalytic activity of Pt–M alloys 22–34 . The intermetallic structure maximizes the number of Pt–M bonds and engenders the intensified electronic interaction (strain and ligand effects) between the Pt and M elements, resulting in an additional activity enhancement.…”

“…Recently, Joo et al . revealed that the intensity of the ligand effect depends on the subsurface atomic arrangement by a combined study of theoretical prediction and model experiments 31 . To exclude the change of strain effect induced by the different crystal structures between alloy and intermetallic phases, they chose the Pt 3 Co composition as a model system.…”

“…The ordered atomic arrangement, which arises from the strong interaction between the two metal elements, leads to excellent chemical stability. During the last decade, intermetallic catalysts whose ORR stability is higher than their random alloy analogs have been reported 27–34 . Interestingly, these intermetallic catalysts have also demonstrated higher intrinsic activity than their alloy counterparts with the same composition 22–26,31 .…”

“…During the last decade, intermetallic catalysts whose ORR stability is higher than their random alloy analogs have been reported 27–34 . Interestingly, these intermetallic catalysts have also demonstrated higher intrinsic activity than their alloy counterparts with the same composition 22–26,31 . In order to further facilitate the research and development of intermetallic catalysts, it is necessary to understand the principles behind the enhanced activity and stability, and catalyst design strategies.…”