Kinetically Controlled, Scalable Synthesis Of Gamma-Feooh Nanosheet Arrays On Nickel Foam Toward Efficient Oxygen Evolution: The Key Role Of In-Situ-Generated Gamma-Niooh

Layered gamma-type iron oxyhydroxide (gamma-FeOOH) is a promising material for various applications; however, its sheet-shaped structure often suffers from instability that results in aggregation and leads to inferior performance. Herein, a kinetically controlled hydrolysis strategy is proposed for the scalable synthesis of gamma-FeOOH nanosheets arrays (NAs) with enhanced structural stability on diverse substrates at ambient conditions. The underlying mechanisms for the growth of gamma-FeOOH NAs associated with their structural evolution are systematically elucidated by alkalinity-controlled synthesis and time-dependent experiments. As a proof-of-concept application, gamma-FeOOH NAs are developed as electrocatalysts for the oxygen evolution reaction (OER), where the sample grown on nickel foam (NF) exhibits superior performance of high catalytic current density, small Tafel slope, and exceptional durability, which is among the top level of FeOOH-based electrocatalysts. Density functional theory calculations suggest that gamma-NiOOH in situ generated from the electrooxidation of NF would induce charge accumulation on the Fe sites of gamma-FeOOH NAs, leading to enhanced OER intermediates adsorption for water splitting. This work affords a new technique to rationally design and synthesize gamma-FeOOH NAs for various applications.