Evaluation of oxygen reduction activity of non-ideal Pt based catalyst thin films

摘要

It is demonstrated that, using thin film electrochemical rotating disc electrode (TF-RDE), oxygen reduction reaction (ORR) activity can be reliably evaluated even from non-ideal (non-uniform) thin platinum-based high-surface area catalyst films. Namely, the classical evaluation (kinetic current density at fixed potential of 0.9 V vs. RHE) is only possible if the catalyst film is close to ideal (uniform and of appropriate thickness), which is sometimes difficult or even impossible to obtain. We propose an alternative way of activity evaluation, which is based on determination of potential at the fixed kinetic current density of 0.1 mAcm~(-2)_(Pt). Performing a case study on ideal and purposely flawed (non-ideal) PtCu/C catalyst films we prove the reliability of the proposed method and a systematically lower error compared to the the conventional fixed-voltage method. We show that Pt-alloy nanoparticles ORR activities can vary from 0.2 to as high as 6.4 mAcm~(-2) by varying the amount of less nobel metal content and by increasing the amount of ordered crystalline PtX_3 phase. In addition, we provide a direct correlation between the two activities.