Highly acid-durable carbon coated Co<inf>3</inf>O<inf>4</inf> nanoarrays as efficient oxygen evolution electrocatalysts

Abstract

Most oxygen evolution reaction (OER) electrocatalysts are not stable in corrosive acids. Even the expensive RuO or IrO , the most acid-resistant oxides, can be dissolved at an oxidative potential. Herein, we realize that the failures of OER catalysts are mostly caused by the weak interface between catalysts and the substrates. Hence, the study of the interface structure between catalysts and substrates is critical. In this work, we observe that the cheap OER catalysts Co O can be more durable than the state-of-the-art RuO if the interface quality is good enough. The Co O nanosheets deposited on carbon paper (Co O /CP) is prepared by electroplating of Co-species and followed by a two-step calcination process. The 1st step occurs in vacuum in order to maintain the surface integrity of the carbon paper and converts Co-species to Co(II)O. The 2nd step is a calcination in ambient conditions which enables the complete transformation of Co(II)O to Co O without degrading the mechanical strength of the Co O -CP interface. Equally important, an in situ formation of a layer of amorphous carbon on top of Co O further enhances the OER catalyst stability. Therefore, these key advances make the Co O catalyst highly active toward the OER in 0.5 M H SO with a small overpotential (370 mV), to reach 10 mA/cm . The observed long lifetime for 86.8 h at a constant current density of 100 mA/cm , is among the best of the reported in literature so far, even longer than the state-of-art RuO on CP. Overall, our study provides a new insight and methodology for the construction of a high-performance and high stability OER electrocatalysts in corrosive acidic environments. 2 2 3 4 2 3 4 3 4 3 4 3 4 3 4 3 4 2 4 2 2 2