Metal-Organic Framework and Carbon Black supported MOFs as dynamic electrocatalyst for oxygen reduction reaction in an alkaline electrolyte

Abstract

The Pt-based expensive catalysts and sluggish kinetics at cathode in oxygen reduction reaction (ORR) hinder the rapid commercialization of fuel cells. The quest for cheap, non-noble metal catalysts to replace Pt-based catalysts has thus become a critical issue in the field of fuel cells. The carbon black (CB) and CB supported catalyst have been explored with the ultimate goal of finding a substitute for Pt-based catalysts in fuel cells. In the present work, we synthesized Zn-based MOF (1), 1 selectivity gives H2O2 followed by two-electron pathways. However, sample 1 modification might be needed to enhance its selectivity for the generation of H2O. Two composites of MOFs with carbon black and 1 were prepared to increase the H2O yield, called 1⊃CB and 1⊃SCB. The electrochemical generation of H2O2 was analyzed by the rotating ring disk electrode (RRDE) using catalyst 1. Following the addition of CB, H2O2 yields decreased from above 93% (1) to 59% and 75% for 1⊃CB and 1⊃SCB, respectively. CB modified catalysts moved towards four-electron pathways due to the conductive nature of CB. Electrochemical Impedance Spectroscopy (EIS) has also been performed to study in detail the conductivity effect of CB and kinetic behavior of ORR in alkaline electrolyte. This research opens up a new path for ORR to advance non-precious metal catalysts based on MOFs. Synopsis: This paper describes how we synthesized carbon Black (CB) supported MOF: Zn-based MOF (1), 1 selectivity gives H2O2 (two-electron pathways). Two composites of MOFs (1⊃CB and 1⊃SCB) were prepared to increase the H2O yield. After addition of CB, H2O2 yields decreased from above 93% (1) to 75% (1⊃SCB) and 59% (1⊃CB).