Increasing the multifunctional oxygenation performance of layered double hydroxides (LDHs) is an exciting but difficult prospect for metal-air batteries. A recent article available as a pre-proof in the journal Applied Surface Science describes the fabrication of a two-dimensional, multifaceted, customized, and polyfunctional oxygen catalyst altered with iron phthalocyanine (FePc) nanoclusters via in situ nickel-cobalt LDH growth on titanium carbide accompanied by FePc adsorption via electrostatic attraction.
Study: FePc nanoclusters modified NiCo layered double hydroxides on Ti3C2 MXene as a highly efficient and durable bifunctional oxygen electrocatalyst for zinc-air batteries. Image Credit: Immersion Imagery/Shutterstock.com
Metal-Air Batteries
Global exploration into sustainable energy generation and storing systems such as metal-air batteries, supercapacitors, and water electrolysis has been prompted by the increasing use of non-renewable fossil fuels and stringent environmental regulations.
Metal-air batteries have attracted great interest due to their cost-effectiveness, high safety, environmental friendliness, and potential high-power density. Unfortunately, several difficulties continue to obstruct their industrialization, including the slow oxygen reduction and evolution processes (ORR/OER), which result in a significant overpotential, inefficient energy transfer, high price, and poor stability. As a result, sensible design and fabrication of cost-effective metal catalysts that benefit both ORR and OER are needed.
What are Layered Double Hydroxides (LDHs)?
Due to their high OER performance, variable geometry, simple synthesis technique, and cheap cost, layered double hydroxides (LDHs) have garnered considerable attention. However, the prevalent aggregation issue arises during the manufacture of pure LDHs, resulting in low electrical conductance and durability, limiting their use in industrial applications.
Appropriate solutions are required in this situation to solve these difficulties. For example, nickel foam, different nano carbons, transition metal nitrides, and carbides (MXenes) have all been used as substrates to increase the OER performance of LDHs by increasing the active surface area and electrical conduction properties. Thus, finding appropriate support is a critical strategy for maximizing the OER effectiveness of nickel cobalt-based LDH (NiCo-LDH).
MXenes as Suitable Supports for LDHs
Due to their unusual two-dimensional composition, strong electrical conductance, and outstanding solubility in water, MXenes such as titanium carbides have a significant deal of promise for use in catalytic reactions. Previously, titanium carbide was used in conjunction with cobalt-based LDHs, which successfully reduced self-aggregation, uncovered more marginal activation centers in CoFe-LDH, and increased the catalytic performance for OER.
The growth of an iron-based LDH on titanium carbide demonstrated remarkable interfacial bonding and electronic bonding with pronounced charge transport, which enhanced not only the structural strength and electrical properties of the nanohybrids but also significantly accelerated the electrochemical operation of FeNi-LDH towards OER. Therefore, MXene materials are a good candidate for LDH as an OER catalyst.
Lately, manifold metal phthalocyanine (MPcs) substances with perfect M-Nx (x=2, 4) functionalities have often been chemically linked to platforms to understand structure-ORR activity connections on the atomic level. This is because direct MPcs deposition onto OER active compounds may also produce unexpected polyfunctional oxygen catalysts. The issue that has to be resolved is how to manage the struggle for active site concentration between ORR and OER to get the best overall oxygen barrier effectiveness.
In Situ Growth of Nickel-Cobalt LDH on Titanium Carbide
In this study, the researchers developed a novel hydrothermal-physical combining approach for growing nickel-cobalt LDH (NiCo-LDH) on the interface of titanium carbide (Ti3C2) and progressively adsorbing FePc through electrostatic contact to create a functionalized oxygen catalyst. The hexagonal NiCo-LDH nanosheets are randomly spread parallel to the plane of the two-dimensional layered architecture of Ti3C2, which is equitably spread with FePc nanoparticles.
Research Findings and Conclusion
This study proposed and fabricated a two-dimensional layered functionalized catalyst using a hydrothermal-physical blending technique based on the logical linkage of the ORR and OER catalytic sites on an electrode surface with an appropriate permeability. The hexagonal NiCo-LDH is grown parallel to the Ti3C2 interface and FePc nanoparticles, which kept the Fe-Nx functionalities distributed evenly throughout the whole catalyst surface.
The existence of electronic contacts between FePc and NiCo-LDH/Ti3C2 altered the electronic structure of the nickel cobalt-based LDH, hence improving the bifunctional catalyst's OER catalytic properties. The effective fabrication of the FePc-NiFeLDH/Ti3C2 catalyst demonstrates a unique approach for the design of durable oxygen electrode electrocatalysts for sustainable energy systems.
Reference
Li, G-L. et al. (2022). FePc nanoclusters modified NiCo layered double hydroxides on Ti3C2 MXene as a highly efficient and durable bifunctional oxygen electrocatalyst for zinc-air batteries. Applied Surface Science. Available at: https://www.sciencedirect.com/science/article/pii/S016943322200705X?via%3Dihub
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