Developing facile approaches to fit in large‐scale fabrication of efficient and durable catalytic electrodes is highly desirable for oxygen electrocatalysis and metal–air batteries. Herein, a strategy based on phase separation and laser induction is proposed to prepare 3D binder‐free integrated electrodes (IEs). The phase separation between a polybenzimidazole (PBI) solution and a coagulation bath containing metal precursors occurs to form a 3D interconnected porous catalyst precursor layer. After drying, IEs are obtained by laser induction, which simultaneously converts PBI into hierarchically porous laser‐induced graphene (HPLIG) and reduces metal precursor to tiny nanoparticles. To demonstrate the versatility of this method, IEs with different HPLIG hybrid catalyst layers and substrates are fabricated. IE‐NiFe/HPLIG and IE‐Co/HPLIG using carbon paper as a substrate exhibit superior oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performance respectively. Flexible IE‐NiCoFe/HPLIG with OER and ORR bifunctionality using carbon cloth as the substrate is applied as an air cathode in rechargeable aqueous Zinc–air batteries (ZABs) and provides a satisfactory power density of 163 mW cm−2 and cycling stability of 1800 h at 10 mA cm−2. The electrode also endows solid ZABs with good flexibility. This work offers an industrially viable solution to the challenge of rapid fabrication of IEs.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/aenm.202200906

3D Binder‐free Integrated Electrodes Prepared by Phase Separation and Laser Induction (PSLI) Method for Oxygen Electrocatalysis and Zinc–Air Battery

Elaborate engineering of heterostructure and composition to regulate the electroactivities remains a pronounced challenge. Herein, a self-supported 2D/2D heterostructure monolith is constructed by interlinked FeCo-hydroxides nanosheets tightly interlacing with aligned Cu0.76Co2.24O4 nanoplates. Due to the well-defined hierarchical nanoarrays and desirable interfacial coupling, the monolithic catalyst can guarantee the rapid charge transfer and mass transport pathways for accelerated surface kinetics, leading to manifestly improved electroactivities and stability toward trifunctional catalysis. Both experimental and theoretical calculations unravel the enriched multimetal active sites for intermediates adsorption and the synergistic interplay of the heterostructure to achieve enhanced catalytic efficiency. Consequently, the heterostructure catalyst contributes to high-performance rechargeable/flexible all-solid-stated Zn-air batteries and water electrolyzer with an ultralow potential of 1.51 V. Moreover, self-powered water splitting system driven by flexible Zn-air batteries delivers a high H2 generation rate. This cost-effective heterostructure monolith could open an intriguing avenue for advancing all-in-one films toward portable energy conversion/storage. 

Interface reinforced 2D/2D heterostructure of Cu-Co oxides/FeCo hydroxides as monolithic multifunctional catalysts for rechargeable/flexible zinc-air batteries and self-powered water splitting

The unremitting exploration of well-architectured and high-efficiency oxygen electrocatalysts is promising to speed up the surface-mediated oxygen reduction/evolution reaction (ORR/OER) kinetics of rechargeable zinc-air batteries (ZABs). Herein, bimetallic CoCu-codecorated carbon nanosheet arrays (CoCu/N-CNS) are proposed as self-supported bifunctional oxygen catalysts. The integrated catalysts are in situ constructed via a simple sacrificial-templated strategy, imparting CoCu/N-CNS with 3D interconnected conductive pathways, abundant mesopores for electrolyte penetration and ion diffusion, as well as Cu-synergized Co-Nx /O reactive sites for improved catalytic activities. By incorporating a moderate amount of Cu into CoCu/N-CNS, the bifunctional activities can be further increased due to synergistic oxygen electrocatalysis. Consequently, the optimized CoCu/N-CNS realizes a low overall overpotential of 0.64 V for OER and ORR and leads to high-performance liquid ZABs with high gravimetric energy (879.7 Wh kg-1 ), high peak power density (104.3 mW cm-2 ), and remarkable cyclic stability upon 400 h/1000 cycles at 10 mA cm-2 . More impressively, all-solid-state flexible ZABs assembled with the CoCu/N-CNS cathode exhibit superior rate performance and exceptional mechanical flexibility under arbitrary bending conditions. This CoCu/N-CNS monolith holds significant potential in advancing cation-modulated multimetallic electrocatalysts and multifunctional nanocatalysts.

Synergistic Bimetallic CoCu-Codecorated Carbon Nanosheet Arrays as Integrated Bifunctional Cathodes for High-Performance Rechargeable/Flexible Zinc-Air Batteries.

The recent and fast-growing trends related to the development of wearable technologies have raised the need for efficient and high-performance energy storage devices having extra features such as flexibility and lightweight. Polymer hydrogels, as viscoelastic lightweight porous nanostructures with tunable surface and structural properties, can play a crucial role in the design of these future energy storage devices. Herein, recent developments and progress in the use of polymer hydrogels to design flexible and wearable energy storage devices are presented and discussed. The 3D structure of polymer hydrogels and porous nanostructures based on these hydrogels provides a platform to design flexible supercapacitors, batteries, and personal thermal management devices. Here, different types of polymer hydrogels are presented, and their main fabrication techniques are reported. Moreover, the main structural properties affecting the energy storage performance of polymer hydrogels are discussed. In addition to recent progress in the design of polymer-hydrogel-based wearable devices, recent developments in polymer hydrogels for flexible applications (batteries, supercapacitors, and thermal energy storage systems) are reviewed in detail. 

Flexible Polymer Hydrogels for Wearable Energy Storage Applications

In this review article, we focus on the design and creation of earth-abundant non-precious metal-coordinated eco-friendly catalysts with high oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performances. The development of a cost-effective, efficient and durable bifunctional ORR and OER electrochemical catalyst is a key for future batteries. So far, precious metals, such as Pt and Ir, have been used as efficient catalysts for the ORR and OER, respectively. However, they are expensive and their deposits on earth are limited, which are the major drawbacks of these metals. One more drawback for the practical application is the sluggish reactions of ORR and OER. Since electroconductivity of promising metal-free catalyst candidates are poor, good electronic supporting materials are needed. Owing to the high conductivity, stability and easy handling, carbon nanotubes are a most promising material. After Introduction, we summarize recent advances in i) carbon nanotube/nanocarbon-based ORR and OER catalysts, ii) metal oxide and others/nanocarbon catalysts for ORR, OER, HER and Zn-air electrodes, as well as iii) computational study for such catalyst reactions. Such studies are highly beneficial for future energy materials design and synthesis in batteries and molecular catalysts with high performances. In this review article, we summarize recent study on the design and creation of carbon nanotube (or other nanocarbon)-based non-precious eco-friendly catalysts with high oxygen reduction, oxygen/hydrogen evolution and Zn-air battery performances. We also focus on computational study for such catalyst reactions. 

Dewei Ye

Papers

Integrated Bifunctional Oxygen Electrodes for Flexible Zinc–Air Batteries: From Electrode Designing to Wearable Energy Storage