Assembling graphene quantum dots on NiFe-LDH provokes ligand effect for electrocatalytic oxygen evolution reaction at industrial-level current density.

Abstract

Electrocatalytic oxygen evolution reaction (OER) plays a key role in water splitting owing to the kinetically more difficult multi-electron transfer process, but the performance is still limited at industrial scale ampere-level current densities. Herein, we develop a surface modification strategy to assemble amino-functionalized graphene quantum dots on NiFe LDH (NiFe LDH/NGQDs) via the coordination between metallic centers with the amino groups in NGQDs. As a nanosized ligand, surface-assembled NGQDs feature sp² conjugation to induce electron redistribution in the coordinated metallic centers, which optimizes OO coupling as a rate-determining step (RDS) in OER. Moreover, edge-aligned NGQDs electrostatically repel from each other to enlarge the interlayered space, allowing abundant OH^- diffusion to facilitate OER kinetics. Such NiFe LDH/NGQDs exhibit an outstanding OER performance with an overpotential of 336mV to achieve a current density of 1.0 A cm^-2 with long-term stability. This work proposes a surface assembly-based catalyst design concept to achieve industrial-level current density in water splitting.