MnO<sub>2</sub>-Templated CuBDC Metal Organic Framework: A Noble-Metal-Free Stable and Efficient pH-Universal Electrocatalyst for Oxygen Reduction Reaction
Murtaza Manzoor Bhat, Murtaza Manzoor Bhat, Feroz Ahmad Sofi, Sajad A. Bhat, Adil Amin Wani, Aamir Yaseen Bhat, Pravin P. Ingole, Mohsin Ahmad Bhat, Mohsin Ahmad Bhat
Abstract
The development of noble-metal-free, efficient, cost-effective, and stable pH-universal electrocatalysts for the oxygen reduction reaction (ORR) is essential for enabling the widespread adoption of ORR-based fuel cells and batteries in practical applications. Herein, we report the design and fabrication of a MnO 2 -supported Cu-Metal Organic Framework (Cu-MOF) as a cost-effective, efficient, stable, and above all a pH-universal ORR electrocatalyst. Specifically, a simple and scalable synthetic approach for the templated synthesis of CuBDC MOF networks over presynthesized MnO 2 nanosheets for the fabrication of CuBDC/MnO 2 composite is presented. The so-crafted CuBDC/MnO 2 composite well-characterized for its chemical, morphological, and electrochemical characteristics is demonstrated to be a pH-universal ORR electrocatalyst exhibiting excellent stability and electrocatalytic performance that is at par with that reported recently for the state-of-the-art noble metal-based ORR catalysts. The CuBDC/MnO 2 composite exhibits a mass transfer limited four-electron pathway ORR at a potential of just 0.74 V versus the reversible hydrogen electrode (RHE), with an overpotential (η ORR ) of 0.45 V under alkaline conditions. The as-fabricated electrocatalyst delivers a specific activity (current per unit area) of −4.58 ± 0.01 mA/cm 2 and the mass activity (current per unit mass) of 8641.50 ± 0.01 mA/mg cat . Our detailed physicochemical and electrochemical investigations clearly establish that the unique synergism among the metal-oxide and MOF components in the CuBDC/MnO 2 composite endows it with unique features that result in the abundant availability and redox accessibility of Cu-redox sites and easy mass transportation of oxygen across an electronically and ionically good conducting [CuBDC/MnO 2 ]/electrolyte interface. The work presented herein signifies a significant advancement toward the development of cost-effective and sustainable ORR electrocatalysts, potentially paving the way for their widespread adoption in clean and affordable electrochemical technologies for storage and conversion of energy.