Constructing hierarchical nanosheet-on-microwire FeCo LDH@Co3O4 arrays for high-rate water oxidation

• Published in: Nano research 2022-12, Vol.15 (12), p.10021-10028
• Main Authors: Tang, Tang, Jiang, Zhe, Deng, Jun, Niu, Shuai, Yao, Ze-Cheng, Jiang, Wen-Jie, Zhang, Lin-Juan, Hu, Jin-Song
• Format: Article
• Language: English
• Subjects: Arrays; Atomic/Molecular Structure and Spectra; Biomedicine; Biotechnology; Cations; Chemistry and Materials Science; Cobalt oxides; Condensed Matter Physics; Current density; Density functional theory; Electrocatalysts; Electrochemistry; Ferric ions; Hydrogen; Hydroxides; Industrial water; Iron; Mass transport; Materials Science; Nanosheets; Nanostructure; Nanotechnology; Oxidation; Photoresponse; Renewable energy; Research Article
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-022-5094-8

Alkaline electrochemical water oxidation powered by renewable energies is a promising and environmentally friendly way to produce hydrogen. The industrial water electrolyzers are commonly operated at a high current density, calling for abundant and durable active sites to participate in. The rational design of hierarchically structured electrocatalysts is thus essential to industrial water electrolyzers. Herein, we develop a Fe 3+ induced nanosizing strategy for fabricating such a hierarchical FeCo LDH@Co 3 O 4 (LDH: layered double hydroxide) nanostructure array for high-rate water oxidation. Density functional theory (DFT) simulations indicate that the introduction of Fe 3+ with a small ion radius and high electrical repulsion in the LDH layer distorted the LDH layer, resulting in a reduced nanosheet size and enabling the formation of a hierarchical structure. Such structure cannot be achieved without the participation of Fe 3+ cations. Benefiting from the significantly enhanced electrochemical surface areas and charge/mass transport due to the hierarchical structure together with the boosted intrinsic activity by electronic modulation of Fe 3+ , such FeCo LDH@Co 3 O 4 electrode can deliver an industrial-level current density of 1,000 mA·cm −2 at a small overpotential of 392 mV for water oxidation. When assembled in a water electrolyzer, it delivers a current density of 100 mA·cm −2 at a low operation voltage of 1.61 V. Powered by solar light, the electrolyzer demonstrates high solar-to-hydrogen efficiency of 18.15% with stable and reproducible photoresponse. These results provide new insights for constructing hierarchical nanostructures for advanced water oxidation and other diverse applications.