Hierarchically Engineered Nanoneedle-Nanosheet Hybrid for High-Performance and Durable Bifunctional Water Splitting

Abstract

In this study, we employed hydrothermally synthesized nanoneedle arrays as a supporting platform, with bimetallic hydroxide nanosheets grown in situ to envelop the nanoneedles, serving as a dual-functional catalyst for overall water splitting. The synthesized CoFe-LDH/Co(OH)2 demonstrates excellent electrocatalytic performance in alkaline media, achieving low overpotentials of 279 mV for the oxygen evolution reaction (OER) and 171 mV for the hydrogen evolution reaction (HER) at a current density of 10 mA·cm−2. The Tafel slopes are remarkably low at 38.31 mV·dec−1 and 67.45 mV·dec−1, respectively. In-situ analysis reveals that the incorporation of Fe species significantly enhances the material’s surface adsorption capacity for -OH and accelerates water dissociation, thereby improving intrinsic OER/HER activity. The electrocatalytically active species were identified as CoOOH and its associated Co oxides. For overall water splitting, the constructed electrolyzer reaches a current density of 10 mA·cm−2 with a low cell voltage of just 1.52 V and retains 99.3% of its initial current density after 50 hours of continuous operation. This study presents a highly competitive strategy for designing bimetallic hydroxide catalysts, offering a promising approach to advancing the development of efficient electrocatalysts for overall water splitting.

Keywords: CoFe-layered double hydroxide, Oxygen evolution reaction, Hydrogen evolution reaction, Overall water splitting