Stabilization of PtRu electrocatalyst by nitrogen doped carbon layer derived from carbonization of poly(vinyl pyrrolidone)

Abstract

Improvements on durability and CO tolerance of the electrocatalyst are crucial for widespread commercialization of direct methanol fuel cells (DMFCs). In this work, we describe a new method to stabilize the PtRu electrocatalyst, in which the PtRu nanoparticles are coated by nitrogen doped carbon layer derived from the carbonization of poly(vinyl pyrrolidone). The coated electrocatalyst shows stable electrochemical surface area (ECSA) and methanol oxidation reaction (MOR) activity after 4200 potential cycles from 0.6 V to 1.0 V vs. RHE; while the non-coated and commercial electrocatalyst lose almost 50% of initial ECSA and MOR activity. Meanwhile, the coated electrocatalyst shows twice higher CO tolerance before and after durability test due to the deceleration of the Ru dissolution proved by the XPS measurement after durability test. The mechanism of the stabilization of Ru was the electron delocalization of Ru caused by the carbonization process of PVP, which changes the electronic structure of Ru and makes Ru difficult to be dissolved. The maximum power density of the coated electrocatalyst is 1.7 times higher than that of commercial CB/PtRu, suggesting the coated electrocatalyst is suitable for real DMFC application. The demonstrated method could be easily extended to obtain extraordinary durability of other electrocatalysts.