In-situ reconstruction of rock-like 3D hierarchical MIL-53(Fe) self-supporting electrode with oxygen vacancy induced ultra-long stable and efficient water oxidation.

[Display omitted] • The 3D hierarchical MIL-53(Fe) was directly in-situ grown on the Fe Foam through the semi-sacrificial template strategy. • The optimized self-supporting electrode can run at 100 mA cm−2 for 520 h without visible decrease in activity. • MIL-53(Fe) structures was completely in-situ self-reconstructed into metal oxyhydroxides with O v after the running OER for 2 h. • DFT calculations reveal that the FeOOH with rich O v transformed from MIL-53(Fe) facilitate the OER catalytic activity. • This work provides a quick and easy method to construct a advanced self-supporting electrodes based on MOFs. The exploitation of efficient, stable and cheap electrocatalyst 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 was developed through a semi-sacrificial strategy. The self-supporting electrode exhibits an excellent OER performance with an overpotential of 328 mV at 100 mA cm−2 in 1 M KOH, which is superior than that of IrO 2 catalyst. Importantly, the optimized self-supporting electrode could operate at 100 mA cm−2 for 520 h without visible decrease in activity. It was also found that the structure of MIL-53(Fe) was in-situ self-reconstructed into oxyhydroxides during OER process. However, the 3D hierarchical open structure assembled with nano-microstructures kept well, which ensured the long-term stability of our self-supporting electrode for OER. Furthermore, density functional theory (DFT) calculations reveal that the FeOOH with rich oxygen vacancy transformed from MIL-53(Fe) plays a key role for the OER catalytic activity. And, the uninterrupted formation of oxygen vacancy during OER process ensures the continuous OER catalytic activity, which is the original source for the ultra-long stability of the self-supporting electrode toward OER. This work explores the way for the construction of efficient self-supporting oxygen electrodes based on MOFs. [ABSTRACT FROM AUTHOR]