(Photo)electrocatalysis of molecular oxygen reduction by S-doped graphene decorated with a star-shaped oligothiophene.

Anastasios Stergiou,Dimitris K Perivoliotis,Nikos Tagmatarchis

doi:10.1039/c9nr01620a

Anastasios Stergiou, Dimitris K Perivoliotis + Show 1 more

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https://doi.org/10.1039/c9nr01620a

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Abstract

Heteroatom-doped graphene-based materials attract great interest as non-metal electrocatalysts for the oxygen reduction reaction (ORR). In this work, a straightforward approach was described to prepare nanoensembles of star-shaped oligothiophene 1 supramolecularly immobilized on sulfur-doped graphene sheets (SG). The 1/SG ensemble was comprehensively characterized by Raman and IR spectroscopy and morphologically imaged by HR-TEM, while the loading of 1 onto SG was estimated by TGA under an inert atmosphere. Based on detailed electrochemical and electrocatalytic assays, 1/SG was proved to be a highly efficient and stable electrocatalyst toward the ORR. The high catalytic activity of 1/SG was attributed to the (a) presence of chemical defects, induced by the insertion of electron rich sulfur within the lattice of SG, (b) existence of structural defects, due to the generation of vacancies along the carbon lattice in SG, and (c) high and homogeneous coverage of the SG surface by the sulfur-rich star-shaped oligothiophene 1. In addition, the optical properties of 1/SG were screened by UV-Vis and steady-state and time-resolved PL and the development of strong photoinduced intra-ensemble electronic interactions within the ensemble was revealed. Exploiting the latter, by photoirradiating 1/SG, a significantly improved photoelectrocatalytic activity towards the ORR was observed.

Highlights

The “oxygen reduction reaction” (ORR) is a fundamental reaction in plant cells catalyzed by specialized metalloenzymes adsorbing the oxygen molecules and dissociating the O–O bond producing sustainable energy for the growth of plants
Recently we showed that linear oligothiophenes, possessing three or nine conjugated rings carrying similar hexyl chains, can be efficiently assembled onto exfoliated graphene via π–π stacking interactions contributing to the development of strong intrahybrid electronic communication upon photoillumination.[27]
The electrochemical data of 1/SG, compared with. Nanoscale those owing to 1, graphene oxide (GO), 1/GO and 5% Pt/C materials, are collectively presented in Electronic supplementary information (ESI), Table S1.† Based on these results, it is clearly demonstrated that the electrocatalytic output for the ORR efficiency of 1/SG was not an overlay of the two individual components, 1 and SG, but rather attributed to a synergistic effect in which the enhanced overall performance is due to the presence of the conjugated thiophene rings in close proximity to the S-doped graphene

Summary

Introduction

The “oxygen reduction reaction” (ORR) is a fundamental reaction in plant cells catalyzed by specialized metalloenzymes adsorbing the oxygen molecules and dissociating the O–O bond producing sustainable energy for the growth of plants. Nanoscale those owing to 1, GO, 1/GO and 5% Pt/C materials, are collectively presented in ESI, Table S1.† Based on these results, it is clearly demonstrated that the electrocatalytic output for the ORR efficiency of 1/SG was not an overlay of the two individual components, 1 and SG, but rather attributed to a synergistic effect in which the enhanced overall performance is due to the presence of the conjugated thiophene rings in close proximity to the S-doped graphene.

Results

Conclusion