(Digital Presentation) Carbon Aerogel Platinum-Praseodymium Oxide Nanocatalyst for Methanol Oxidation in 0.5 M Sulfuric Acid
Authors: Prits Alise-Valentine , Nerut Jaak , Kasuk Heili , Koel Mihkel , Sepp Silver , Valk Peeter , Aruväli Jaan , Koppel Miriam , Mikli Valdek , Volobujeva Olga , Lust Enn 
Published: July 2022

Electrooxidation of methanol is an essential topic in developing direct methanol fuel cells, and numerous catalyst materials have been studied for this application. 1–3 Among other materials, the platinum-based composite catalysts containing rare earth metal oxides on various support materials have shown promising properties for methanol oxidation and implementation for direct methanol fuel cells.1–3

In this study, platinum-praseodymium oxide nanocatalyst on carbon aerogel support for methanol oxidation was synthesized. The material was electrochemically characterized using rotating disk electrode, cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy methods. X-ray diffraction, specific surface area measurements, thermogravimetric analysis, and high-resolution scanning electron microscopy with energy dispersive X-ray analysis were used to determine the physical properties of the material.
The catalyst was synthesized by depositing platinum4 on a pyrolyzed organic aerogel doped with Pr(NO3)3
5,6. Synthesized nanocatalyst material contained 21 wt% of Pt and 20 wt% of PrOx. This material has micro-mesoporous structure with surface area of 230 m2 g−1, micropore area of 70 m2 g−1, total pore volume of 0.62 cm3 g−1 and micropore volume of 0.032 cm3 g−1. Pt and PrOx particles were uniformly dispersed on the supporting carbon aerogel-derived material.
Electrochemical measurements showed that the studied material has an electrochemically active surface area of 54 mPt
2 gPt
−1, which is noticeably higher than that for commercial Pt-Vulcan catalyst (17 mPt
2 gPt
−1) and comparable with similar composite catalyst materials containing rare earth metal oxides (from 45 mPt
2 gPt
−1 up to 61 mPt
2 gPt
−1).3 For methanol electrooxidation the synthesized material showed high current density peaks in both anodic (310 A gPt
−1) and cathodic (240 A gPt
−1) potential sweeps. These current densities are higher than measured for commercial Pt-Vulcan catalyst (for the peaks in both anodic (178 A gPt
−1) and cathodic (167 A gPt
−1) potential sweeps). Furthermore, the synthesized material demonstrated the ability of preserving higher catalytic activity (0.33 A gPt
−1) than the commercial Pt-Vulcan catalyst (0.07 A gPt
−1) after working on a fixed potential of ‒0.2 V vs RHE for an extended period of time (30 min). While these results outstand the catalytic activity of some similar catalyst materials containing praseodymium,1,7,8 higher current densities on both cathodic and anodic potential sweep have been measured with Pt-PrOx catalyst deposited on carbon black Vulcan XC-72R.3 These characteristics show good suitability of the developed nanocatalyst for methanol oxidation in direct methanol fuel cells.
This study shows the potential of nanocatalysts containing rare earth metal oxides and catalyst on the carbon aerogel support for methanol electrooxidation. These materials could be further investigated for the electrooxidation for ethanol or other organic fuels.

Acknowlegements

This work was supported by the EU through the European Regional Development Fund TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), the Estonian Energy Technology Program: SLOKT10209T “Nanomaterials – research and applications (NAMUR)” project 3.2.0304.12-0397and Personal Research Grant PRG676.

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