Bimetallic (Mn/Co) oxide nanoparticles supported over a covalent organic framework for oxygen evolution reaction

Abstract

To meet the current energy demands finding a clean, sustainable and efficient energy source is highly needful to replace fossil fuels. In response to this demand, developing an efficient H2 liberating system that would produce enormous hydrogen by electrochemical water splitting (to break water into O2 and H2) would be a cost-effective route. However, oxygen evolution reaction (OER) has slow kinetics and often associate with high overpotential. Hence OER is the key process to determine the overall efficiency of the water-splitting reaction. A catalyst can reduce this overpotential to minimize the energy consumption in the water-splitting reaction. Therefore, developing a cheap, readily synthesizable catalyst is always promising in the splitting of water. To date, researchers have used noble metal catalysts (Pt, Ir, Ru, RuO2, IrO2, PtO2, etc.) to split the water, which often requires a sizable cost. Hence, first-row transition metal nanoparticles (NPs) as the catalysts would be an alternating cheap source. However, increasing the surface area and active sites of the metal catalyst could also boost its performance. Therefore, reducing the size of metal NPs using a suitable capping agent is also extremely needful. Microporous Covalent Organic Framework (COF) is an important class of chemically and thermally stable designer porous material. Notably, one can tune its pore sizes and functionalities as per the requirement of a particular application by judicious selection of monomers. This makes COF excellent porous support to dock the metal NPs. Thus, COF helps in forming very smaller size metal NPs with high surface area and hence enhances COF-supported metal NP catalyst performance. Herein, porous pyridyl-rich COF supports the Mn and Co-based NPs for the electrochemical OER reaction in an alkaline medium. The nanocomposite showed a decent activity with 340 mV overpotential toward OER at a current density of 10 mA/cm2.