Optimized porous nanostructure of carbon fibers enabling excellent stability of Pt-based catalysts for oxygen reduction reaction

Abstract

Facile synthesis of highly-dispersed Pt-based electrocatalysts on porous carbon supports with strong durability is extremely desirable for oxygen reduction reaction but remains challenging. The influence of pores in carbon supports on the stability and activity of catalysts is ambiguous and needs to be elucidated. Targeting this aim, herein, we prepared a series of carbon nanofibers with tunable pore diameter and specific surface area using the resorcinol-formaldehyde (RF) resins as a model system. Homogeneous composite precursors composed of RF resins and silica colloids were synthesized by the surfactant-assisted simultaneous polycondensation of RF resins and tetraethylorthosilicate (TEOS). The diameter of the pores induced by removal of silica could be controllable tailored through thermal treatment of the composite under various target temperatures. Pt3Co alloy nanoparticles loaded on the as-synthesized porous carbon nanofibers were prepared by an optimized wet-impregnation method. The experimental results indicated that the carbon nanofibers with pore size distribution focused on ∼1.27 nm and ∼2.34 nm provided the best stability without limiting current density decay, and negative shift of half-wave potential (E1/2) and mass activity (MA) loss of Pt after 20000 potential cycles are relatively mild. Conversely, negative shift of 21 mV, 15 mV and 22 mV in E1/2 and mass activity loss of 51.8%, 30.2% and 33.0% were observed for the Pt3Co nanoparticles supported on MC-60, MC-100 and MC-140 matrices which have pore size distribution focused on ∼2.73 nm, ∼2.73 nm as well as ∼4.66 nm, and ∼4.66 nm, respectively. This work demonstrates the importance of micropores and small mesopores for activity and long-term stability enhancement of carbon supported Pt-based electrocatalysts.