Preparation and structural optimization of carbon-encapsulated PtRu nanoparticles on 3D nitrogen-doped carbon frameworks for highly efficient and durable methanol oxidation catalysis

Pt-based electrocatalysts struggle to achieve a balance between excellent activity and robust long-term stability towards methanol oxidation reaction (MOR). Herein, ultrafine PtRu nanoparticles (NPs) are successfully encapsulated into carbon shells and dispersed on 3D nitrogen-doped carbon frameworks (NrGO7-OCNTs3). Rational modifications are performed to regulate the structure of PtRu NPs and their distribution on the NrGO7-OCNTs3. As a result, when the atom ratio of Ru to Pt is 0.5 and the reduction temperature is 300 °C, the obtained PtRu_0.5@C/NrGO7-OCNTs3 catalyst exhibits optimum performance towards MOR. The catalyst's electrochemical surface area and mass activity are up to 244.0 m²·g_Pt⁻¹ and 1508 A·g_Pt⁻¹, respectively, 2.7 and 3.0 times more than commercial PtRu/C catalysts. PtRu_0.5@C/NrGO7-OCNTs3 catalyst also shows good resistance to CO with significantly lower desorption potential compared to the PtRu/C catalyst. Moreover, the long-term stability of the catalyst is improved dramatically. After a 7200 s continuous test, the current density of PtRu_0.5@C/NrGO7-OCNTs3 catalyst reaches 86.7 A·g_Pt⁻¹, about 4.0 times higher compared to the PtRu/C catalyst. These characteristics are mainly attributed to the excellent support architecture, the crucial role of carbon confinement in particle stability, and the strong synergistic effect between Pt and Ru atoms. Pt loading of the obtained catalyst is only half of that of the commercial PtRu/C catalyst, thereby achieving substantial cost savings. This facile approach will greatly promote the large-scale production of Pt-based catalysts with high activity and stability at the industrial level, and facilitate the widespread adoption of DMFCs.