Two-dimensional ultrathin donor-acceptor Co-based metal organic framework nanoplates for efficient electrocatalytic water splitting.

It is key to develop novel economical and effective non-noble metal bifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting cells. Herein, a series of novel two-dimensional (2D) ultrathin donor-acceptor Co-based metal organic framework nanoplates (U-DA-CoMOF-NPs) as bifunctional HER/OER catalysts have been designed and fabricated based on a donor-acceptor strategy. Density functional theory calculations demonstrate that the fabricated U-DA-CoMOF-NPs are fine donor-acceptor pairs having HOMO-LUMO localizations and a HOMO-LUMO gap of 2.60 eV and give the Gibbs free energy for a reasonable OER mechanism. Additionally, changes in anions can affect the physicochemical characterizations and HER/OER performance of the fabricated U-DA-CoMOF-NPs. As a result, the fabricated U-DA-CoMOF-NPs-1 using NO 3 − as an anion exhibits the optimal HER/OER performance in alkaline solution thanks to the thinnest nanoplate thickness, the largest surface area and hierarchical mesoporous structure. Moreover, a self-assembled overall water splitting cell with U-DA-CoMOF-NPs-1/NF as both cathode and anode achieves a low potential of 1.65 V and a high cycling stability at 10 mA cm−2 for at least 15 h. The present study offers an option to design and fabricate other cost-effective donor-acceptor MOF-based catalysts for water splitting cells. • A series of U-DA-CoMOF-NPs have been fabricated with a donor-acceptor strategy. • The HOMO positioning is on Tdc, LUMO localization is at Tpt and a gap is 2.6 eV. • Co–N has more positive catalytic ability for OER than pyridinic-N and thiophene-S. • The representative U-DA-CoMOF-NPs-1 exhibits the optimal HER/OER performance. • A U-DA-CoMOF-NPs-1/NF cell shows a low potential and high stability at 10 mA cm−2. [ABSTRACT FROM AUTHOR]