Adsorption and On-Site Transformation of Transition Metal Cations on Ni-Doped AlOOH Nanoflowers for OER Electrocatalysis

AlOOH has long been used as excellent adsorbent for removal of heavy metal cations from wastewater. Herein we report one-pot synthesis of carboxylic-functionalized Ni-doped AlOOH nanoflowers (AlOOH NFs) with high adsorptive capability toward various transition metal cations, and more importantly, the AlOOH NFs adsorbed with various transition metal cations were for the first time directly used as electrocatalyst for oxygen evolution reaction (OER). By simply manipulating the initial metal cation concentration and their molar ratio, the OER catalytic performance of the resulting catalysts could be modulated. The lowest overpotential at a current density of 10 mA cm(-2) prepared from AlOOH NFs adsorbed with Fe-III and Ni-II is 0.32 V in 0.1 M KOH and 0.275 V in 1.0 M KOH. Such AlOOH-supported electrocatalyst demonstrates remarkable stability, which shows no evident increase of the overpotential at 10 mA cm(-2) after 2 h of steady electrolysis at an overpotential of 0.42 V. The excellent OER electrocatalytic activity originates from the on-site formation of ultrafine FeOOH and NiOOH nanoclusters with average sizes below 3 nm during the electrocatalytic process. As such, we demonstrate the workability of using functionalized AlOOH NFs as a bifunctional platform for adsorption of transition metal cations and easy preparation of efficient and cost-effective OER catalysts.