A surface-mounted MOF thin film with oriented nanosheet arrays for enhancing the oxygen evolution reaction

Developing efficient and inexpensive oxygen evolution reaction (OER) catalysts is one of the critical issues in energy storage and conversion technology. Herein, an oriented thin film of 3-D MOF Co/Ni(BDC)2TED (BDC = 1,4-benzenedicarboxylate; TED = triethylenediamine) nanosheet arrays is first obtained on Cu foam by a liquid-phase epitaxial layer-by-layer growth approach. The obtained thin film of bimetallic MOF nanosheet arrays has preferred growth with [001]-orientation and strong adhesion on the substrates without the use of binder materials, which provides more accessible active sites for electrocatalytic performance. The OER activity of such surface-mounted MOF nanosheet arrays can be optimized effectively via tuning the thicknesses and Co/Ni ratios. The Co/Ni(BDC)2TED grown on Cu foam with 40 cycles at a Co/Ni ratio of 1/1 shows superior OER activity with required overpotentials of 260 and 287 mV to achieve current densities of 10 and 50 mA cm−2 and excellent stability. The experiments and theoretical calculations reveal that the synergistic effect of Co/Ni and rich metal sites dominated by nanosheet interfaces improve the electrocatalytic activity. This work provides more insight into the OER activity of the MOF thin film as an electrode material and presents a new strategy for developing promising highly efficient electrocatalysts in practical applications.