l‑Lysine-Functionalized Reduced Graphene Oxide as a Highly Efficient Electrocatalyst for Enhanced Oxygen Evolution Reaction

As functional molecules, amino acids have attracted great attention in the field of material sciences due to their interactive sites. New studies have shown the electrocatalytic activity capability of amino-acid-functionalized graphene oxide (GO) toward the oxygen evolution reaction (OER). The improved active sites and further tunable and huge surface area after l-lysine functionalization on reduced graphene oxide (Ly-rGO) offer significant opportunities for further enhancement in the OER activity. Herein, the functionalization of GO with terminal nitrogen-containing groups (l-lysine) results in efficient and stable electrocatalytic activity for OER with a lower overpotential of 0.33 V at 10 mA cm^–2 and a lower Tafel slope of 80 mV dec^–1. Electrochemical impedance spectroscopic of Ly-rGO also shows a lower R_ct = 29.58 Ω and an excellent current stability for 5000 s at an onset potential of 1.29 V vs SCE in 0.5 M KOH. Morphological studies based on high-resolution transmission electron microscopy confirm that the size of Ly-rGO is ∼5 nm. X-ray photoelectron spectroscopic analysis confirms the surface functionalization of GO by lysine (Ly-rGO) from the binding energies of C–N, C–O, and C–C. From this perspective, our findings emphasize the usefulness of metal-free amino-acid-functionalized carbon-based electrocatalysts for OER, which is an important water-splitting reaction, and demonstrates that they may be keys toward enhancement in activities.