Cu(II)-Based Coordination Polymer as a Pristine Form Usable Electrocatalyst for Oxygen Reduction Reaction: Experimental Evaluation and Theoretical Insights into Biomimetic Mechanistic Aspects.

Abstract

As the postsynthesis-processed metal-organic material-based catalysts for energy applications add additional cost to the whole process, the importance of developing synthesized usable pristine catalysts is quite evident. The present work reports a new Cu-based coordination polymer (Cu-CP) catalyst to be used in its pristine form for oxygen reduction reaction (ORR) application. The catalyst was characterized using single-crystal X-ray diffraction, field emission scanning electron microscopy, and X-ray photoemission spectroscopy. The Cu-CP exhibits admirable electrocatalytic ORR activity with an onset potential of 0.84 V versus RHE and a half wave potential of 0.69 V versus RHE. As revealed by the density functional theory-based computational mechanistic investigation of the electrocatalytic ORR process, the electrochemically reduced Cu(I) center binds to the molecular O2 through an exergonic process (ΔG = -6.8 kcal/mol) and generates the Cu(II)-O2•- superoxo intermediate. Such superoxo intermediates are frequently encountered in the catalytic cycle of the Cu-containing metalloenzymes in their O2 reduction reaction. This intermediate undergoes coupled proton and electron transfer processes to give OH- in an alkaline medium involving H2O2 as the intermediate. The electrocatalytic performance of Cu-CP remained stable even up to 3000 cycles. Overall, the newly developed Cu-CP-based electrocatalyst holds promising potential for efficient biomimetic ORR reactivity, which opens new possibilities toward the development of robust coordination polymer-based electrocatalysts.