l‑Lysine-Functionalized Reduced Graphene\nOxide as a Highly Efficient Electrocatalyst for Enhanced Oxygen Evolution\nReaction

Abstract

As\nfunctional molecules, amino acids have attracted great attention\nin the field of material sciences due to their interactive sites.\nNew studies have shown the electrocatalytic activity capability of\namino-acid-functionalized graphene oxide (GO) toward the oxygen evolution\nreaction (OER). The improved active sites and further tunable and\nhuge surface area after l-lysine functionalization on reduced\ngraphene oxide (Ly-rGO) offer significant opportunities for further\nenhancement in the OER activity. Herein, the functionalization of\nGO with terminal nitrogen-containing groups (l-lysine) results\nin efficient and stable electrocatalytic activity for OER with a lower\noverpotential of 0.33 V at 10 mA cm^–2 and a lower\nTafel slope of 80 mV dec^–1. Electrochemical impedance\nspectroscopic of Ly-rGO also shows a lower <i>R</i>_ct = 29.58 Ω and an excellent current stability for 5000\ns at an onset potential of 1.29 V vs SCE in 0.5 M KOH. Morphological\nstudies based on high-resolution transmission electron microscopy\nconfirm that the size of Ly-rGO is ∼5 nm. X-ray photoelectron\nspectroscopic analysis confirms the surface functionalization of GO\nby lysine (Ly-rGO) from the binding energies of C–N, C–O,\nand C–C. From this perspective, our findings emphasize the\nusefulness of metal-free amino-acid-functionalized carbon-based electrocatalysts\nfor OER, which is an important water-splitting reaction, and demonstrates\nthat they may be keys toward enhancement in activities.