Nitrogen-Doped Hollow Carbon Spheres as a Support for Platinum-Based Electrocatalysts

Abstract

Platinum and platinum alloys supported on carbon materials are the state of the art electrocatalysts for the essential oxygen reduction reaction (ORR) in low-temperature fuel cells. The limited stability of such materials under the often detrimental operation conditions of fuel cells still remains a critical issue to improve. In this work, we explore the impact of nitrogen-doped carbon supports on the activity and stability of platinum-based fuel cell catalysts. We present a nitrogen-doped mesostructured carbon material, nitrogen-doped hollow carbon spheres (NHCS), as a support for platinum-based electrocatalysts. A detailed study of the electrochemical activity and stability was carried out for two Pt@NHCS materials i.e., as-made material (Pt@NHCS) with a Pt particle size smaller than 2 nm and the corresponding material after thermal treatment at 850 degrees C (Pt@NHCS_ΔT) with a Pt particle size of ca. 23 nm. Activity in the ORR was studied by rotating disc electrode (RDE) thin-film measurements, and electrocatalyst stability was evaluated by accelerated aging tests under simulated startstop conditions. The performance of the NHCS-based materials was compared to the two corresponding nitrogen-free materials as well as to a standard Pt/Vulcan catalyst. The underlying degradation mechanisms of Pt@NHCS materials were investigated via identical location electron microscopy. Our results conclusively show that nitrogen doping of the carbon supports can offer benefits for achieving high initial mass activities due to improved high platinum dispersion; however, it was not found to necessarily lead to an improvement of the catalyst stability

Template-free ultraspray pyrolysis synthesis of N/Fe-doped carbon microspheres for oxygen reduction electrocatalysis

“…43 The A 398 /A TOT ratio decreases from 74% for GH710, to 27% for GH900, thus suggesting that the proportion of pyridinic nitrogen decreases upon annealing in favor of pyrrolic/quaternary nitrogen, in agreement with previous observations from several groups. 16,44 Finally, iron was also detected in both GH710 and GH900 XPS spectra. The integrated area of the Fe 2p 3/2 peak (see ESI †) was used to calculate Fe/C atomic ratios (Table 1) which were found to decrease upon annealing.…”

Importance of non-intrinsic platinum dissolution in Pt/C composite fuel cell catalysts

“…[25][26][27][28][29] Furthermore, the detrimental role of nanoparticle coalescence 5 and its circumvention by designing a microporous carbon support (exploiting the so-called confinement effect) has been reported. [30][31][32] Platinum dissolution has been extensively studied before -either in the form of a polycrystalline disk [33][34][35][36] or as a nanoparticulate catalyst. [3][4][5][6]29,[37][38][39][40] It has been shown that the electrochemical dissolution of Pt is predominantly a transient phenomenon occurring due to the interplay of Pt oxidation and reduction processes.…”

“…Finally, some studies involving N-doped carbon supports only showed an increased initial activity but no particular improvement in catalyst stability. 31 Even though performed in a simple half-cell configuration, these studies shed new light on the extensive complexity of the catalyst composite dissolution process. This calls for further investigation before real catalyst layers should be designed.…”

Study of Preparation, Growth Mechanism and Catalytic Performance of Carbon Based Embedded Silver Nano Composite Materials

“…These excellent properties make it widely used in many fields. For example, it is often designed to be applied in gas adsorbent [5], catalyst supports [6], lithium-ion batteries [7], super capacitor [8] and so on.…”