Climbing over the activity volcano correlation by biomimicking Vitamin B12: A co phthalocyanine pyridine axial ligand coordinated catalyst for the reduction of molecular oxygen

Jorge Riquelme, Karinna Neira, José F. Marco, Patricio Hcrmosilla, Diego Vencgas, Walter Orellana, Ingrid Ponce, José H. Zagal, Federico Tasca

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Citations (Scopus)

Abstract

CoN4 macrocyclic complexes like Co phthalocyanines (CoPc) have been extensively studied as electrocatalysts for the ORR but they preferentially promote the 2-e reduction of O2 to give peroxide. In contrast, Vitamin B12, a naturally occurring CoN4 macrocyclic molecule alkaline media promotes the 4-electron reduction of O2 to H2O. Vitamin B12 possesses an imidazole axial back ligand and this seems to be the reason for its higher activity and selectivity for the 4-e reduction of O2. To test this hypothesis, we synthesized a CoPc axially coordinated to pyridine anchored to carbon nanotubes (Co-Py-CNT). The Co center is therefore coordinated to 5 nitrogens as in Vitamin B12. The modified CoPcPy containing catalytic material was characterized by EPR and XPS spectroscopy. DFT calculations. According to our results the pyridine back ligand increases the Co-O2 binding energy, making it more similar to VitB12, favoring the splitting of the O-O bond. The back ligand then plays a crucial role in modifying Co-O2 binding energy which is a well know reactivity descriptor. A further evidence of this dramatic change in reactivity of CoPc by the presence of the "Py" back ligand is that it moves from the weak binding leg of a volcano correlation to the strong leg of the volcano. This might explain why nature uses a back ligand in cytochrome c to catalyze the ORR.

Original languageEnglish
Title of host publicationECS Transactions
EditorsM. Shao, G. Brisard, M. Bayachou, N. M. Markovic, M. B. Vukmirovic, P. Zelenay, K. Sasaki, S. R. Brankovic, J. Zhang, J. X. Wang
PublisherElectrochemical Society, Inc.
Pages111-121
Number of pages11
Volume85
Edition12
ISBN (Electronic)9781607685395
ISBN (Print)9781607688402
DOIs
Publication statusPublished - 1 Jan 2018
EventElectrocatalysis 9: Symposium in Honor of Radoslav Adzic - 233rd ECS Meeting - Seattle, United States
Duration: 13 May 201817 May 2018

Publication series

NameECS Transactions
Number12
Volume85
ISSN (Print)1938-6737
ISSN (Electronic)1938-5862

Conference

ConferenceElectrocatalysis 9: Symposium in Honor of Radoslav Adzic - 233rd ECS Meeting
Country/TerritoryUnited States
CitySeattle
Period13/05/1817/05/18

ASJC Scopus subject areas

  • General Engineering

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