Electrodeposited graphene nanosheets supported Ni(OH)2-NiO electrocatalysts for enhanced oxygen evolution

Conductive graphene nanosheets boost oxygen evolution electrocatalysis. • Electrochemically assisted deposition forms porous Ni(OH) 2 /NiO onto freestanding graphene. • Low overpotential of 260 mV at 10 mA cm −2 and Tafel slope of 41 mV dec −1 . • Macroscopic model indicates faster *OOH formation with transfer coefficient of 0.74 Developing low-cost oxygen evolution reaction (OER) catalysts with efficient charge transport and accessible active sites is essential for alkaline water electrolysis. Here we report an electrochemically assisted technique (EAT) to deposit highly dispersed Ni(OH) 2 species on the surface of freestanding graphene (Gr) without deliberate surface functionalization, where a transient SiO 2 -derived framework assists the deposition process of Ni(OH) 2 , followed by heat treatment and alkaline etching to form an intimately contacted Gr@eNi(OH) 2 -NiO composite. On one hand, Gr enables the highly dispersed distribution of Ni(OH) 2 /NiO species and improves the accessibility of active sites for the OER. On the other hand, Gr provides good electrical conductivity and rapid charge-transfer kinetic, leading to high catalytic activity. In 1 M KOH, Gr@eNi(OH) 2 -NiO delivers an overpotential of 260 mV at 10 mA cm −2 and Tafel slope of 41 mV dec −1 , together with stable operation in alkaline electrolyte. Macroscopic kinetics analysis based on current-overpotential fitting further suggests an enhanced potential response of the *OOH-forming step, consistent with improved OER kinetics enabled by Gr-deposit coupling. This work provides a practical route to integrate Ni hydroxide/oxide phases with Gr scaffolds for efficient alkaline water oxidation. Download: Download high-res image (334KB) Download: Download full-size image