Nature-Inspired Catalysts: A New Era for Water-Splitting Technology

Jyoti Bhattacharjee and Subhasis Roy*

Department of Chemical Engineering, University of Calcutta, A. P. C. Road, Kolkata, India.

Corresponding Author E-mail: subhasis1093@gmail.com

Copy the following to cite this article: Bhattacharjee J, Roy S. Nature-Inspired Catalysts: A New Era for Water-Splitting Technology. Mat. Sci. Res. India;21(2).

Copy the following to cite this URL: Bhattacharjee J, Roy S. Nature-Inspired Catalysts: A New Era for Water-Splitting Technology. Mat. Sci. Res. India;21(2). Available from: https://bit.ly/4dAGIdW

Introduction

Water-splitting has emerged as a beacon of hope in the quest for sustainable energy solutions. This process, which involves separating water into hydrogen and oxygen using a catalyst, promises to produce clean hydrogen fuel. The potential of this technology is immense, yet one of the critical challenges lies in developing efficient and cost-effective catalysts. Interestingly, the most promising advancements in this field are increasingly being drawn from nature itself. In this concern, the interest in finding clean, sustainable energy solutions has increased in the past decade. Hydrogen represents one of the most promising new green energy carriers with huge future potential. Water splitting, where water decomposes into hydrogen and oxygen upon the application of electricity, is one major avenue to produce hydrogen ¹. Traditional electrolyzers, however, always use precious metals and non-eco-friendly materials; therefore, developing such traditional electrolyzers raises concerns regarding their sustainability and environmental impact. This editorial provides an overview of the progress on catalytic membranes for water-splitting electrolyzers and covers recent developments, materials, and future directions of this most significant area of research. Naturally occurring enzymes like those in photosystem II offer blueprints for developing highly efficient catalysts ^1,2. By insertion of bio-inspired catalysts into biopolymer membranes, one can realize very significant catalytic enhancements ^1,2.

Electrolysis of water is a sustainable approach to obtaining uncontaminated hydrogen fuel. Thus, successful membrane-less electrolysis of water for clean hydrogen production is challenging in developing efficient and environmentally benign catalytic membranes. Biopolymers, particularly chitosan, cellulose, and alginate, are among the most outstanding due to their high abundance and biodegradability. In other words, these materials can provide a versatile scaffold for constructing catalytic membranes. An excellent beneficial situation has been achieved in the catalytic activity by functionalizing biopolymers with catalytic nanoparticles, such as nickel-iron-layered double hydroxides (NiFe LDH) or cobalt phosphate. In one study, chitosan-based membranes were used with NiFe LDH placement, exhibiting higher OER activity and stability under the applied conditions. The natural cross-linking agent, tannic acid, even improved the mechanical properties of such membranes ^2,3.

Hierarchical Structure Design

This porosity is hierarchical, characteristic of nature in building structures such as leaf veins and diatoms, which enhance water transport across the membranes and maximize the catalytic surface area. Biotemplating techniques inspired by these natural structures can, therefore, allow for the preparation of complex pore geometries that can equally transform water molecules with reasonable efficiency. Using hierarchically porous diatom frustules to increase the surface area of biopolymer membranes gives enhanced catalytic efficiency. Membranes with such bio-inspired inclusions can yield good replicas of nature’s activities. For instance, it was demonstrated that quite dramatic improvements in electron transfer rates and catalytic activity were brought about by enzyme mimics, such as those for photosystem II, and redox-active proteins like cytochromes. A cytochrome c-entrapped bioinspired membrane showed much better electron transfer than a native one, leading to better catalytic activity in the hydrogen evolution reaction ^3,5.

The hybridization of biopolymers with nanomaterials, especially metal-organic frameworks (MOFs) or carbon-based nanomaterials, such as graphene oxide, results in nanocomposite membranes with higher conductivity and catalytic activity. The techniques based on the layer-by-layer assembly principle open horizons for depositing catalytic materials under complete control. The prepared alginate-graphene oxide-MOF nanocomposite membrane showed superior stability and catalytic activity because the nanocomposite membrane had a lamellar structure, which allowed effective charge transfer. It is essential to employ eco-friendly membrane production and synthesis methods. Biosynthesis of the nanoparticles by plant extract or microbial routes might be greener alternatives to conventional chemical methods. The second point identified was in the aspect of minimally hazardous solvent-free or water-based synthesis methods. Embedding redox-active proteins, such as cytochromes, into the membrane matrix could further facilitate electron transfer processes of higher orders of magnitude, thereby increasing the overall efficiency of the electrolyzer. These proteins can be immobilized onto the membrane surface or integrated within the biopolymer matrix to establish a biohybrid system with improved catalytic properties. Biopolymer-nanomaterial hybrids offer an exciting platform to create a variety of high-performance catalytic membranes. Nanocomposite membranes realize the unique features of these two kinds of components, leading to synergistic enhancements^3,4.

Hybrids of Biopolymers and Nanoparticles

This is the case in synthesizing hybrid membranes, where biopolymers are integrated with metal-organic frameworks or carbon-based nanomaterials, such as graphene oxide, to enhance conductivity and catalytic activity. Indeed, MOFs have tuneable porosity and high surface area, making them excellent supports for catalytic nanoparticles, while graphene oxide can enhance electron transport within the membrane. Gold nanoparticles embedded in cellulose membranes using various impregnation methods proved highly catalytic and green in performance^4,5.

It requires increased durability and stability in the long-term operation of catalytic membranes. Polydopamine coatings make it biocompatible, providing chemical and biological protection to the membrane. Moreover, including biological system-inspired self-healing materials may extend the membrane lifespan. Fouling-resistant cellulose membrane coated with polydopamine exhibits high catalytic activity even after a long period of use. Integrating catalytic membranes with renewable energy sources, like solar-powered electrolyzers, is a representative instance of a real sustainable hydrogen production pathway. Use of photocatalysts to catch sunlight for increasing water cleavage can allow an increase in efficiency. This initiated the development of biohybrid systems that combine the advantages of natural photosynthetic mechanisms with biological components, for instance, algae, in favor of the synergies conferred by nature with catalytic membranes. The operational conditions must, therefore, be rigorously tested for eco-friendly catalytic membrane performance^5,6.

Key performance metrics include ionic conductivity, mechanical stability, and chemical degradation resistance. Most innovative materials that look very promising in the labs tend to disappoint regarding real-world application, scaling, and long-term stability. This further raises the question of the economic feasibility of mass production of such green membranes. Researchers will hence have to come up with cheaper methods of synthesis that do not affect the performances of the membranes. Besides, lifecycle assessments are necessary for estimating the environmental footprint of these materials from production to disposal to ascertain their positive contributions towards achieving sustainability goals.

Conclusion and Future Prospects

Nature’s catalytic mastery provides a blueprint for developing sustainable energy solutions. Researchers are creating innovative materials to revolutionize water-splitting technology by mimicking these processes. Although obstacles remain, the progress achieved thus far underscores the power of biomimicry and nanotechnology in building a clean energy future. As research progresses, the vision of a hydrogen-based economy fueled by efficient and environmentally friendly water splitting becomes increasingly attainable. Advanced simulation and modeling techniques form the keystone in optimizing the design and performance of catalytic membranes, and they are also discussed in this study.  Molecular dynamics simulations (MD) simulations can reveal information about the interaction between water molecules and the membrane surface, guiding the optimization of the design for enhanced performance. From the atomic level of detail in molecular dynamics simulations of the behavior of water and ions, key parameters that ultimately determine catalytic activity and transport properties could be realized ^7,8.

Using the density Functional Theory (DFT), the catalytic efficiency of the different biopolymer-catalyst ensembles could be predicted ^1-4. By gaining insight into the mechanisms of reaction at an atomic level, particularly their electronic structure, better catalysts can be designed, and the properties of the biopolymer matrix can be tuned accordingly. The development of environmentally benign catalytic membranes should consider their integration with renewable energy sources for sustainable hydrogen production. A biohybrid membrane followed by algae and attached photocatalysts has been designed for a solar-driven electrolyzer with a high rate of hydrogen production, proving the scope for sustainable hydrogen generation [7-9]. Eco-friendly development of catalytic membranes, which will be used for sustainable hydrogen production, is developed using biological raw materials. This write-up’s Major drivers include innovations based on biopolymers on membranes, hierarchical structures, bioinspired catalysts, nanocomposites, green synthesis techniques, and durability enhancements. Integrating these membranes with renewable energy sources offers the potential to move bench science closer to a clean energy future.

Despite the promising advancements, several challenges remain. The stability of synthetic catalysts under real-world conditions is a critical issue. While many catalysts perform well in laboratory settings, their efficiency often declines in practical applications. Researchers are working to develop more robust catalysts that can withstand harsh operating conditions without degradation. Moreover, scaling up these technologies for industrial applications presents another significant challenge. The production methods for many advanced catalysts are often complex and costly. Simplifying and making these processes economically viable is essential for commercializing water-splitting technology. Integrating artificial intelligence and machine learning in catalyst design holds great potential. These technologies can accelerate discovering and optimizing new catalysts by analyzing vast data and identifying patterns that human researchers might overlook. This approach could lead to the rapid development of highly efficient and durable catalysts.

References

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