Oxygen Electrocatalysis on Mixed-Anion Perovskite Compounds in Alkaline Media
Authors: Miyahara Yuto , Miyazaki Kohei , Yoshida Kyosuke , Kondo Yasuyuki , Yokoyama Yuko , Abe Takeshi 
Published: December 2020

Enhancement of oxygen reduction and evolution reaction (ORR and OER) performance has been considered to play a key role for the development of next-generation energy storage devices such as metal-air batteries and water electrolyzers. Recently, mixed-anion compounds have been found to be highly efficient bifunctional electrocatalysts for ORR and OER[1,2]. Our group has been also clarified that layered perovskite oxychloride Sr2Co1
−

x
Fe
x
O3Cl serves as a good bifunctional catalyst, whose OER activity outperformed that of Ba0.5Sr0.5Co0.8Fe0.2O3
−δ
[3]. While detailed mechanism of its enhanced OER activity has been discussed previously[4], that of ORR has not been evaluated in detail, even though ORR pathway is generally considered to be much more complicated. Moreover, further exploration of highly active bifunctional mixed-anion perovskites has to be continued for better understanding of oxygen electrocatalysis on mixed-anion perovskite compounds. In the present research, therefore, we focused on the evaluation of ORR pathway for Sr2Co1
−

x
Fe
x
O3Cl, and oxygen electrocatalysis on other mixed-anion perovskite compounds in alkaline media.

Solid-state method was applied to the synthesis of Sr2Co1
−

x
Fe
x
O3Cl and other mixed-anion perovskites. Electrochemical measurements were conducted by a three-electrode cell with a rotating disk electrode (RDE). Glassy carbon RDEs coated by a catalyst layer consisting of catalysts, Vulcan XC-72 (Cabot), and AS-4 (Tokuyama) were used for the working electrode. Pt wire and reversible hydrogen electrode were used for the counter and reference electrodes, respectively. Oxygen-saturated 1 mol dm−
3 KOH solution was used for ORR activity tests, and Argon-saturated 1 mol dm−
3 KOH solution containing 5 mmol dm−
3 H2O2 was used for the activity tests of peroxide reduction reaction (PRR). Peroxide decomposition rates of Sr2Co1
−

x
Fe
x
O3Cl were performed by measuring evolved oxygen gas in the same manner as previously described[5].

While the highest OER activity was observed at x = 0.2, ORR activity of Sr2Co1
−

x
Fe
x
O3Cl was monotonously decreased with increase of Fe doping. Figure 1 shows decomposition rates of Sr2Co1
−

x
Fe
x
O3Cl in 1 mol dm−
3 KOH. Surprisingly, their HO2
− decomposition rate was higher than those of cobalt-based perovskite oxides such as LaCoO3, whose ORR activity was comparable to those of oxychlorides. Further discussion about ORR pathway of Sr2Co1
−

x
Fe
x
O3Cl, and oxygen electrocatalysis of other mixed-anion perovskites will be provided at the conference.

Figure 1. H2O2 decomposition rates of Sr2Co1
−

x
Fe
x
O3Cl powders.

References

[1] A. Miura, C. Rosero-Navarro, Y. Masubuchi, M. Higuchi, S. Kikkawa, and K. Tadanaga, Angew. Chem. Int. Ed., 55 (2016) 7963.

[2] M. A. Ghanem, P. Arunachalam, A. Almayouf, and M. T. Weller, J. Electrochem. Soc., 163 (2016) H450.

[3] Y. Miyahara, K. Miyazaki, T. Fukutsuka, and T. Abe, Chem. Commun., 53 (2017) 2713.

[4] Y. Miyahara, K. Miyazaki, T. Fukutsuka, and T. Abe, 232nd ECS Meeting, (2017) A1-30.

[5] H. M. Zhang, Y. Shimizu, Y. Teraoka, N. Miura, and N. Yamazoe, J. Catal., 121 (1990) 432.

Figure 1