Comparison of the Catalytic Activity of Carbon, Spinel-Based, and Carbide Materials in the Na-Air Battery

Evelina Faktorovich-Simon,Amir Natan,Emanuel Peled,Diana Golodnitsky

doi:10.3389/fmats.2019.00249

Abstract

Rechargeable sodium-oxygen batteries have attracted much interest in recent years, owing to their high theoretical specific energy, and the abundance of sodium. The material of which the cathode is constructed influences the performance of the battery. In this study, we show that low-surface-area glassy carbon (GC) cannot operate for more than four consecutive cycles, whereas high-surface-area carbon materials, such as Black Pearl 2000 carbon (BP 2000), significantly increase the number of cyclic- voltammetry runs, without current reduction. NiCo2O4 was previously considered a promising material for the cathode. However, its activity was not compared with the only carbon-based electrode. Here we compare the electrochemical performance of four different NixCoyOz powders to BP 2000, XC72R, and SB carbon. The highest activity was obtained with the use of a powder, which contained 45% NiCo2O4, 10% CoO, 30% metallic nickel and 15% metallic cobalt. We believe that the metallic nickel and cobalt phases are responsible for this high catalytic activity. Accelerated stress tests of XC72R, BP 2000, SB, and TiC powders, after 100 cyclic-voltammetry cycles, revealed that TiC exhibited the greatest loss of reduction peak area (~57%) during the test, indicating the highest loss of catalytic activity. It also exhibited higher loss of oxidation peak area than Vulcan XC72R (~68% vs. ~35%), but lower than BP 2000 (~90%) and SB carbon (~72%). The reason for such a high degradation probably comes from strong surface changes or loss of adhesion of the catalyst powder to the GC electrode during the AST. It was suggested that in most cases, it is the OER process, which exhibits stronger deterioration.

Highlights

Rechargeable sodium-oxygen batteries have attracted much interest in recent years, thanks to their high theoretical specific energy, lower charge overpotential than lithium-oxygen batteries and the abundance of sodium
We have evaluated the durability of TiC electrode by estimating its catalytic properties after 100 oxygen-reduction reaction (ORR)/oxygen-evolution reaction (OER) cycles
Molecular dynamic simulation studies of adsorption energies of oxygen and NaO2 molecules on the surface of the catalyst components could be helpful for the explanation of the findings mentioned above

Summary

Introduction

Rechargeable sodium-oxygen batteries have attracted much interest in recent years, thanks to their high theoretical specific energy, lower charge overpotential than lithium-oxygen batteries and the abundance of sodium. It was shown that this cell can be cycled several times (Peled et al, 2011). Another advantage of the Na-air system is that, in contrast to lithium, sodium does not dissolve in aluminum (0.003%) and this enables the use of aluminum as a light and low-cost hardware material, especially for thin bipolar plates. Catalytic Activity of Carbon, Spinel, Carbide product, in sodium-oxygen batteries, at least three different discharge products have been reported: sodium superoxide, peroxide dihydrate, and dehydrated sodium peroxide (NaO2, Na2O2·2H2O, and Na2O2) (Hartmann et al, 2014; Kwak et al, 2015; Pinedo et al, 2016). NaO2-based batteries show low overpotentials and high coulombic efficiencies, while in Na2O2based batteries, notably higher overpotentials are reported (Hartmann et al, 2013; Kim et al, 2016; Pinedo et al, 2016)

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Results

Conclusion