Electric‐Field Assisted Hydrolysis‐Oxidation of MOFs: Hierarchical Ternary (Oxy)hydroxide Micro‐Flowers for Efficient Electrocatalytic Oxygen Evolution

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2022-02, Vol.18 (6), p.e2104863-n/a
• Main Authors: Li, Xia, Hou, Mengxia, Qu, Xinbo, Zhang, Yunqiang, Li, Mei
• Format: Article
• Language: English
• Subjects: Chemical composition; CoNiFe (oxy)hydroxide; electric‐field assisted alkaline hydrolysis‐oxidation; Electrocatalysts; Energy conversion; Flowers; Hydrolysis; Hydroxides; Iron; Kinetics; Metal-organic frameworks; micro‐flowers; Nanotechnology; Oxidation; oxygen evolution reaction; Oxygen evolution reactions; Three dimensional flow; Water splitting
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202104863

Water oxidation is the key process of electrocatalytic water splitting owing to its inherently slow kinetics. The ingenious design of microstructures for oxygen evolution reaction (OER) catalysts is an important way to accelerate the kinetics of the water splitting reaction. In this work, a facile electric‐field assisted alkaline hydrolysis‐oxidation strategy is proposed to prepare 3D layered micro‐flowers in situ constructed from ultra‐thin CoNiFe (oxy)hydroxide (CoNiFe‐OH) hexagonal plates by using Co/Ni/Fe metal‐organic frameworks (MOFs) as sacrificial templates and metal sources. The growth of the ballflowers can be accurately controlled by matching the hydrolysis rate of MOFs templates and the coprecipitation rate of metal ions. More importantly, continuous oxidation voltage can drive transformation of some hydroxides into oxyhydroxide with abundant oxygen vacancies. Benefiting from the open structure with multiple electroactive sites and optimized chemical composition, the layered CoNiFe‐OH micro‐flowers show appealing OER electrocatalytic performance with a low overpotential of 207 mV@10 mA cm−2 and robust durability over 60 h. This work provides a strategy to prepare non‐noble hierarchical nanostructured electrocatalysts for electrochemical energy conversion. A simple electric‐field assisted alkaline hydrolysis‐oxidation method is used to transform the bulk metal‐organic frameworks grown on nickel foam into hierarchical micro‐flowers formed by tightly stacked ultra‐thin CoNiFe (oxy)hydroxide hexagonal plates. The unique structure and optimized chemical composition of CoNiFe (oxy)hydroxide micro‐flowers result in excellent oxygen evolution performance and long‐term stability.