Ordered PtCo Intermetallics Featuring Nitrogen‐Doped Carbon Prepared by Surface Coating Strategy for Oxygen Reduction Reaction

Abstract

Improving the activity and stability of Pt‐based electrocatalysts is essential for large‐scale commercial applications of fuel cells. The ordered Pt‐based alloy nanomaterials encapsulated by coating have attracted significant attention. Here, we displayed a surface coating strategy to synthesize structurally ordered PtCo alloy catalysts featuring nitrogen‐doped carbon (NC). Experimental results reveal that the sample with appropriate dopamine feeding content shows enhanced oxygen reduction activity and stability, which exhibits a mass activity of 1.36 mA ⋅ mg−1Pt and specific activity of 1.98 mA ⋅ cm−2, superior to those of excessive or low dopamine adding content samples and commercial Pt/C catalyst. The enhanced electrocatalytic performance of this catalyst was attributed to the combined effect including the protection of suitable thickness NC shells, strong electronic interaction and high ordering degree. In this work, the surface coating strategy provides available references to further improve the oxygen reduction performance of PtM alloy catalysts.

Design principles for the synthesis of platinum–cobalt intermetallic nanoparticles for electrocatalytic applications

“…The removal of protective layers is often necessary to activate catalysts if such a strategy is used. 92,93 For example, 3 nm L1 0 -PtCo intermetallic NPs can be synthesized via a surface coating strategy. 76,93 The dopamine coating was firstly introduced on the carbon-supported Pt NPs via p-p bond conjugation and subsequently converted into a carbon shell, resulting in the adsorption of Co ions.…”

“…92,93 For example, 3 nm L1 0 -PtCo intermetallic NPs can be synthesized via a surface coating strategy. 76,93 The dopamine coating was firstly introduced on the carbon-supported Pt NPs via p-p bond conjugation and subsequently converted into a carbon shell, resulting in the adsorption of Co ions. 93 Silica coating was then applied to the surface to prevent particle sintering during annealing.…”

“…76,93 The dopamine coating was firstly introduced on the carbon-supported Pt NPs via p-p bond conjugation and subsequently converted into a carbon shell, resulting in the adsorption of Co ions. 93 Silica coating was then applied to the surface to prevent particle sintering during annealing. Such a rigid silica shell is effective in limiting the size growth but it also requires HF etching in the posttreatment steps.…”

“…Besides the above case studies where Pt atom was used, carbon 76,93 and ionic liquids 106 were also used to make the shell. For example, dopamine was used to coat the carbonsupported Pt NPs and subsequently converted into nitrogendoped carbon shell via pyrolysis under H 2 atmosphere.…”

“…Similarly, multiple structural factors help to enhance the durability of the Pt-Co intermetallic electrocatalysts, which include the degree of ordering, 83,122 composition, 111,130,133 particle size, 33,83,94 and core-shell structure. 28,30,93,100 The impact of structural ordering of the Pt-Co catalyst on metal (Pt and Co) dissolution and re-deposition as well as the associated durability under PEMFC operational conditions was revealed by a microscopic study. 83 Since the oxidation of surface Pt atoms is often the cause for the dissolution of Pt-based NP electrocatalysts, eliminating the reactive corner and edge sites of L1 0 -PtCo NPs by the addition of a less reactive metal such as Au could improve the durability by blocking the oxidation of Pt at these sites.…”