High Voltage Enabled Stable Cobalt Species Deposition on MnO 2 for Water Oxidation in Acid.

The design and maintenance of high active sites in acidic environment is vital and challenging for oxygen evolution reaction (OER). Here, we find that the obtained CoO 2 under high applied potential can be stable on MnO 2 host in acidic environment, which may act as an effective means to solve the instability of cobalt-based electrocatalyst. The significant improvement of acidic OER activity (6.9 times) and stability (46.4 times) of 90-Co-MnO 2 (treated by molten salt with more Co deposition sites) demonstrates the advantages of this approach. In-situ Raman and Pourbaix diagram suggest that the enhanced performance derives from the stable presence of CoO 2 at the voltage greater than 1.8 V versus RHE. However, when the potential is less than 1.8 V, the corresponding other cobalt specie is too unstable to facilitate OER. Density functional theory (DFT) calculations reveal that the deposited cobalt oxides can act as active sites, thus, effectively reducing the reaction energy barrier of the rate-determining step (RDS). This work provides a new perspective for enhancing the stability of cobalt-based electrocatalyst. In the future, the dual consideration of applied potential and stable species of active element in Pourbaix diagram may be a new direction for developing acid-stable electrocatalysts. This article is protected by copyright. All rights reserved.