Role of Specific N-Containing Active Sites in Interconnected Graphene Quantum Dots for the Enhanced Electrocatalytic Activity towards Oxygen Evolution Reaction

Abstract

Electrochemical water oxidation is a dynamic and basal approach for several energy conversion technologies such as solar fuels and metal–air batteries. Herein, we report a novel ‘nitrogen’ (N) enriched interconnected graphene quantum dots (C‐GQDs) as efficient oxygen evolution electrocatalyst, a potential candidate to replace the noble metal OER electrocatalysts. Interestingly, C‐GQDs deliver a current density of 10 mAcm‐2 at 350 mV, a small Tafel slope of 55 mV/dec and outstanding durability which is much superior to the state‐of‐the‐art precious RuO2. More precisely, the unexpected behaviour of graphene quantum dots towards oxygen evolution reaction (OER) is attributed to the interconnection through N‐rich framework (25 %) among the discrete particles. Predominantly, in the pyridine N‐oxide, N acts as nucleophilic site and pyridinic N develops p‐ type doping, responsible for enhanced the OER electrocatalytic activity. The co‐existence of both pyridinic N and pyridine N‐oxide N induces charge redistribution through π‐π delocalization to reduce the *OOH thermodynamic energy barrier. We hope that our study will encourage to develop more efficient electrocatalysts with more effective doping or surface functionalized structure by understanding the dopant nature.

Electrochemistry in Carbon‐based Quantum Dots

“…N‐CQDs are efficient oxygen evolution electrocatalyst owning to the interconnection and N‐surface functionalization . Besides, CQDs based nanocomposites, such as Co 3 O 4 /N‐CQDs, CoP/CQDs, NiCo 2 P 2 /CQDs, MnO 2 /CQDs and CoFe/CQDs can also improve the OER performance. HER, as one of half reactions of electrocatalytic water splitting, is one of the most efficient ways to produce clean fuel (hydrogen) from water.…”

Computational Studies on Carbon Dots Electrocatalysis: A Review

“…The coexistence of pyridine N and pyridine N-oxide N causes charge redistribution through π-π delocalization and reduces the *OOH thermodynamic energy barrier. [136] In addition to single N-doping, Shin et al developed a metalfree porous graphene frame which embedded N, S co-doped CDs as a dual-functional oxygen electrocatalyst for metal-air batteries. The synergistic effect of double N and S doping reduces the activation barrier of oxygen adsorption on CDs, providing numerous N and S defect sites as electrocatalytic active centers, and meanwhile the graphene synergistically enhanced the conductivity.…”

Recent Progress in the Development of Advanced Functionalized Electrodes for Oxygen Evolution Reaction: An Overview

“…After the fabrication process, TA-metal complex film composites were considered as the new-type OER active electrocatalysts [ 18 ]. Interestingly, a nitrogen-enriched graphene quantum dots (C-GQDs) catalyst was developed with an efficient electrocatalytic activity, and the charge distribution of pyridine and pyridine N-oxide is induced through the π–π delocalization process, which could encourage their OER activity [ 19 ]. Surendran et al [ 20 ] hydrothermally synthesized the spherically nanostructured carbon-enriched cobalt phosphide multi-functional electrode for water electrolyzer studies, and reported the current density of 10 mA cm −2 @ 1.63 V. Qian et al [ 21 ] prepared a cost-effective, larger specific surface area with high electrically conductive natured MWCNTs for the making of a thermo-electrochemical (TEC) catalyst by the electrochemical deposition (EPD) method.…”