Effect of Reheating Treatment on Oxygen-Reduction Activity and Stability of Zirconium Oxide-Based Electrocatalysts Prepared from Oxy-Zirconium Phthalocyanine for Polymer Electrolyte Fuel Cells

Abstract

Zirconium oxide-based electrocatalysts with multi-walled carbon nanotubes as electroconductive support (ZrC x N y O z /MWCNT) were prepared by oxidation of oxy-zirconium phthalocyanine under low oxygen partial pressure and examined as new non-platinum cathodes for polymer electrolyte fuel cells. The effect of reheating treatment of ZrC x N y O z /MWCNT in the temperature range from 900 to 1200 • C for 1 h under nitrogen atmosphere on the activity and stability of the oxygen-reduction reaction (ORR) was investigated. The reheating treatment at 1000 • C enhanced the ORR activity because of the formation of oxygen vacancies, which might act as active sites for the ORR. The reheating treatment at temperatures above 1100 • C, however, led to the formation of carbonitrides which are unstable under cathode conditions, resulting in decrease in the ORR activity. The reheating treatment significantly increased the durability of ORR at both low (0.6 V vs. reversible hydrogen electrode (RHE)) and high (1.2 V) potential.The reheating treatment at higher temperatures promoted graphitization of the deposited carbon. Because the degradation in the high-potential region mainly originates from corrosion of the carbon materials, graphitization would be effective to improve the durability.

Enhancement of Electrode Stability Using Platinum–Cobalt Nanocrystals on a Novel Composite SiCTiC Support

“…In regards to the metal catalyst, platinum has been the most used metal in this type of fuel cells. Nevertheless, the scarcity and high cost of this metal is a hindrance, and new materials that decrease the cost without compromising the catalytic activity would be beneficial [20][21][22] . Therefore, binary and ternary Pt-alloys that exhibit a higher activity than Pt alone have been developed [23][24][25] .…”

ZrO2Based Oxygen Reduction Catalysts for PEMFCs: Towards a Better Understanding

“…10 In order to increase the very low catalyst dispersion (i.e., the electrochemically active surface area per gram of catalyst) obtained with the above synthesis approaches, methods to synthesize highly dispersed Zr oxide nanoparticles supported on carbon black were investigated. 12,[17][18][19] For these materials, the ORR activity was correlated with synthesis-specific parameters, such as temperature, gas composition, and heat-treatment time during synthesis, 4,5,9,[20][21][22][23] but a systematic quantitative comparison of the effect of the synthesis conditions on the ORR activity has not yet been conducted and is subject of the present work.…”

Oxygen Reduction Durability and Activity of Tantalum Oxide-Based Electrocatalysts for Cathode of Polymer Electrolyte Fuel Cells

“…We already demonstrated that the reheating treatment was useful to increase the stability of the deposited carbon [6]. Therefore, at first we tried to prepare the nano-sized oxide-based particles with high dispersion.…”