The most well-known electrocatalyst for oxygen evolution reaction (OER) have been noble metals or combination of them such as ruthenium, and/or iridium.¹ Due to their cost and scarcity, however, there is a persistent search for alternative materials. Metal organic frameworks (MOFs) have recently attracted significant attention due to their versatility and stability in wide range of environments that allow for post-synthetic modifications and functionalization. This tunability of MOFs has given way to the development of exceptional electrocatalyst that can have comparable performance to noble metals, and mitigate the issues found in them.²

In this study we investigated the OER performance of the zirconia-based MOF, UiO-66, as a support for metal oxides such as CoO_x, MnO_x and TiO_x. UiO-66 has previously been used as a support for catalyst such as molybdenum, and has rendered comparable catalytic performance to that of platinum carbon for the hydrogen evolution reaction (HER).³ Having a MOF support for catalysts, such as metal oxides, can be ideal due to the well-defined MOF surrounding that will allow them to function as catalyst, but protect them from agglomeration at high temperatures.

We synthesized samples containing UiO-66, graphene oxide (GO) and cobalt oxide (CoO_x) using the solvothermal method. Electrochemical characterization revealed that the hybrid CoO_x@UiO-66/GO affords an excellent catalytic activity for OER with an onset potential of 1.6 V versus RHE, comparable to that of Ir and Ru-based catalysts.² Additionally, this study contains discussions on the factors of the high OER activity through a series of physical characterizations of the hybrid catalyst.

References:

1. Lee, Y., Suntivich, J., May, K. J., Perry, E. E. & Shao-Horn, Y. Synthesis and Activities of Rutile IrO 2 and RuO 2 Nanoparticles for Oxygen Evolution in Acid and Alkaline Solutions. doi:10.1021/jz2016507
2. Aijaz, A. et al. Co@Co3O4 Encapsulated in Carbon Nanotube-Grafted Nitrogen-Doped Carbon Polyhedra as an Advanced Bifunctional Oxygen Electrode. Angew. Chemie - Int. Ed. 55, 4087–4091 (2016).
3. Yang, J. et al. Porous Molybdenum Phosphide Nano-Octahedrons Derived from Confined Phosphorization in UIO-66 for Efficient Hydrogen Evolution. Angew. Chemie - Int. Ed. 55, 12854–12858 (2016).