A homogeneous cobalt complex mediated electro and photocatalytic O2/H2O interconversion in neutral water

Abhishek Saini; Chandan Das; Surabhi Rai; Aritra Guha; Dependu Dolui; Piyali Majumder; Arnab Dutta

doi:10.1016/j.isci.2023.108189

A homogeneous cobalt complex mediated electro and photocatalytic O₂/H₂O interconversion in neutral water

iScience. 2023 Oct 12;26(11):108189. doi: 10.1016/j.isci.2023.108189. eCollection 2023 Nov 17.

Authors

Abhishek Saini¹, Chandan Das¹, Surabhi Rai^{1

2}, Aritra Guha¹, Dependu Dolui¹, Piyali Majumder¹, Arnab Dutta^{1

3

2}

Affiliations

¹ Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
² National Center of Excellence in CCU, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
³ Interdisciplinary Program in Climate Studies, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.

Abstract

The O₂/H₂O redox couple is vital in various renewable energy conversion strategies. This work delves into the Co(L-histidine)₂ complex, a functional mimic of oxygen-carrying metalloproteins, and its electrochemical behavior driving the bidirectional oxygen reduction (ORR) and oxygen evolution (OER) activity in neutral water. This complex electrocatalyzes O₂ via two distinct pathways: a two-electron O₂/H₂O₂ reduction (catalytic rate = 250 s^-1) and a four-electron O₂ to H₂O production (catalytic rate = 66 s^-1). The formation of the key trans-μ-1,2-Co(III)-peroxo intermediate expedites this process. Additionally, this complex effectively oxidizes water to O₂ (catalytic rate = 15606 s^-1) at anodic potentials via a Co(IV)-oxo species. Additionally, this complex executes the ORR and OER under photocatalytic conditions in neutral water in the presence of appropriate photosensitizer (Eosin-Y) and redox mediators (triethanolamine/ORR and Na₂S₂O₈/OER) at an appreciable rate. These results highlight one of the early examples of both electro- and photoactive bidirectional ORR/OER catalysts operational in neutral water.

Keywords: Coordination chemistry; Physical inorganic chemistry.