A Selective Copper Based Oxygen Reduction Catalyst for the Electrochemical Synthesis of H2O2 at Neutral pH

Bas van Dijk; Rick Kinders; Thimo H Ferber; Jan P Hofmann; Dennis G H Hetterscheid

doi:10.1002/celc.202101692

A Selective Copper Based Oxygen Reduction Catalyst for the Electrochemical Synthesis of H₂O₂ at Neutral pH

ChemElectroChem. 2022 Feb 11;9(3):e202101692. doi: 10.1002/celc.202101692. Epub 2022 Feb 2.

Authors

Bas van Dijk¹, Rick Kinders¹, Thimo H Ferber², Jan P Hofmann², Dennis G H Hetterscheid¹

Affiliations

¹ Leiden Institute of Chemistry Leiden University P. O. Box 9502 2300 RA Leiden, The Netherlands.
² Surface Science Laboratory Department of Materials and Earth Sciences Technical University of Darmstadt Otto-Berndt-Strasse 3 64287 Darmstadt Germany.

Abstract

H₂O₂ is a bulk chemical used as "green" alternative in a variety of applications, but has an energy and waste intensive production method. The electrochemical O₂ reduction to H₂O₂ is viable alternative with examples of the direct production of up to 20% H₂O₂ solutions. In that respect, we found that the dinuclear complex Cu₂(btmpa) (6,6'-bis[[bis(2-pyridylmethyl)amino]methyl]-2,2'-bipyridine) reduces O₂ to H₂O₂ with a selectivity up to 90 % according to single linear sweep rotating ring disk electrode measurements. Microbalance experiments showed that complex reduction leads to surface adsorption thereby increasing the catalytic current. More importantly, we kept a high Faradaic efficiency for H₂O₂ between 60 and 70 % over the course of 2 h of amperometry by introducing high potential intervals to strip deposited copper (^depCu). This is the first example of extensive studies into the long term electrochemical O₂ to H₂O₂ reduction by a molecular complex which allowed to retain the high intrinsic selectivity of Cu₂(btmpa) towards H₂O₂ production leading to relevant levels of H₂O₂.

Keywords: copper complexes; electrocatalysis; homogeneous catalysis; hydrogen peroxide; oxygen reduction.