The Origin of the Ultra-Long Stability of Rock-Like 3d Hierarchical Mil-53(Fe) Self-Supporting Electrode Toward Efficient Water Oxidation

Abstract

Rationally exploiting efficient, stable and cheap electrocatalysts for oxygen evolution reaction (OER) is very significant to the development of energy technology. In this study, Fe-based metal-organic frameworks (MIL-53(Fe)) self-supporting electrode with a 3D hierarchical open structure is developed through the semi-sacrificial strategy. The self-supporting electrode exhibits an excellent OER performance with an overpotential of 341 mV at 100 mA cm-2 in 1 M KOH, outperforming the IrO2 catalyst. Importantly, the optimized self-supporting electrode can run at 100 mA cm-2 for 520 h without visible decrease in activity. It is also found that the MIL-53(Fe) structures are in situ self-reconstructed into oxyhydroxides during OER process. However, the 3D hierarchical open structure assembled with nano-microstructures is kept well, which ensures the long-term stability of our self-supporting electrode for OER. Furthermore, density functional theory (DFT) calculations reveal that the FeOOH with rich O vacancy transformed from MIL-53(Fe) plays a key role for the OER catalytic activity. And the uninterrupted formation of O vacancy during OER process guarantees the continuous OER catalytic activity, which is the original source for the ultra-long stability of the self-supported electrode toward OER. This work paves the way for the construction of efficient self-supporting oxygen electrodes based on MOFs.

Keywords: oxygen evolution reaction, Self-supporting electrode, Metal-organic framework, Hierarchical open structure, Semi-sacrificial strategy