Carbon dots with tunable concentrations of trapped anti-oxidant as an efficient metal-free catalyst for electrochemical water oxidation

Abheek Datta,Sutanu Kapri,Sayan Bhattacharyya

doi:10.1039/c6ta04737h

Abstract

Carbon dots, containing keto-groups as active sites and the highest abundance of an anti-oxidant, 5-hydroxymethyl-2-furaldehyde, efficiently catalyse oxygen evolution reaction in alkaline medium and generate 10 mA cm−2at 0.21 V overpotential..

Highlights

With increased microwave reaction time, the concentration of 5-HMF inside the Carbon dot (C-dot) decreases at the cost of different furan derivatives which decreases the oxygen evolution reaction (OER) activity
During continuous electrolysis beyond 10 min, 5-HMF gets converted to 2,5-diformylfuran entities, which increases the catalytically active sites and thereby maintains the OER activity of the C-dots for at least 4 h
We show that the water-dispersible pristine C-dots are excellent OER catalysts providing one of the highest J and lowest h to date

Summary

Introduction

The impending energy crisis in today's world is driving the search for mature, clean and renewable energy in the form of fuels and water oxidation to molecular oxygen has attracted immense attention in this respect.[1,2,3] water electrolysis is thermodynamically unfavorable since the standard reduction potential EOo 2=H2O per electron transferred is 1.23 V versus reversible hydrogen electrode (RHE) and the associated free energy (DG) is 237.2 kJ molÀ1.4,5 The OER in the natural enzyme photosystem II is catalyzed by cubane-like Mn4CaOx active sites, in a physiological pH environment with a moderate overpotential (h) of 0.3–0.4 V.5,6 Developing a nature mimicking, stable OER catalyst for arti cial photosynthesis is a formidable challenge and a body of recent work is available in the search for efficient, robust and inexpensive electro-catalysts.[2,7,8] A majority of the OER catalysts known to date suffer from limitations such as low current density (J) and overpotential of several hundred millivolts. Developing a nature mimicking, stable OER catalyst for arti cial photosynthesis is a formidable challenge and a body of recent work is available in the search for efficient, robust and inexpensive electro-catalysts.[2,7,8] A majority of the OER catalysts known to date suffer from limitations such as low current density (J) and overpotential of several hundred millivolts. Precious metals such as Ru and Ir metals are known to demonstrate reliable OER activities,[9] the.

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