Stability and Activity of Cobalt Antimonate for Oxygen Reduction in Strong Acid
Lan Zhou, Hao Li, Yungchieh Lai, Matthias H. Richter, Kevin Kan, Joel A. Haber, Sara R. Kelly, Zhenbin Wang, Yubing Lu, R. Soyoung Kim, Xiang Li, Junko Yano, Jens K. Nørskov, John M. Gregoire
Abstract
Guided by computational Pourbaix screening and high-throughput experiments aimed at the development of precious-metal-free fuel cells, we investigate rutile CoSb2O6 as an electrocatalyst for oxygen reduction in 1 M sulfuric acid. Following 4 h of catalyst conditioning at 0.7 V vs RHE, operation at this potential for 20 h yielded an average current density of −0.17 mA cm–2 with corrosion at a rate of 0.04 nm hour–1 that is stoichiometric with catalyst composition. Surface Pourbaix analysis of the (111) surface identified partial H coverage under operating conditions. The Sb active site has an HO* binding free energy of 0.49 eV, which is near the peak of the kinetic 4e– ORR volcano for transition-metal oxides in acidic conditions. The experimental demonstration of operational stability and computational identification of a reaction pathway with favorable energetics place rutile CoSb2O6 among the most promising precious-metal-free electrocatalysts for oxygen reduction in acidic media.