Actual image of a continuous photocatalytic hydrogen generation reactor and accessory setup. Credit: Elsevier, International Journal of Hydrogen Energy
Environmental pollution and affordable clean energy are the two main sustainable development goals set by the United Nations General Assembly in 2015. All countries are setting targets for decarbonization by 2050 and increasing energy consumption. use of green hydrogen to reduce the annual electricity consumption burden. .
Industries and research groups have jointly collaborated to increase the production of green hydrogen and reduce production costs. In 2023, we saw global energy crises in large parts of Europe during the war, leading to high prices and shortages of liquefied natural gas and worsening climate change.
Typically, green hydrogen is generated via electrolyzers and photocatalytic water splitting. There are some obstacles to the commercial production of green hydrogen, such as high production costs, photocatalyst stability, catalyst performance, and the use of seawater.
The photocatalytic solar water division has opened a new window of opportunity for low-cost green hydrogen production while respecting environmental protection. Sunlight is abundant in the environment, and choosing the appropriate photocatalyst with long-term stability and high performance can improve the production and reduce the price of green hydrogen.
Notably, all photocatalysts available for the production of hydrogen by water splitting are in the form of powdered nanoparticles, causing losses and metal attacks, leading to lower photocatalytic activity and an impact on operating costs. . Additionally, powdered nanoparticle photocatalyst systems operate only in batch mode and are unable to control the rate of hydrogen production.
Hydrogel photocatalyst based on alginate with their confined water Credit: Elsevier, International Journal of Hydrogen Energy
The powdered nanoparticle photocatalyst contains semiconductors that can leach into water bodies and harm the ecological pyramid. Metal-organic structures were proposed to support the alloy nanoparticles to prevent metal aggregation during the reaction and to stimulate the catalytic activity.
The team led by Professor Kajari Kargupta from the Nanoengineering and Sustainable Energy Laboratory, Department of Chemical Engineering, Jadavpur University, India, has now developed a recyclable and eco-friendly 3D organic alginate hydrogel. environment encapsulated in a ball-type photocatalyst. The study is published in the International Journal of Hydrogen Energy.
These kinds of hydrogel photocatalysts based on 3D metal-organic structure can provide a continuous constant rate of hydrogen. The toxic effect of the semiconductor is minimized through encapsulation with sodium alginate, a food grade material.
Sodium alginate is the preferred biopolymer for photocatalyst-encapsulated millispheres. It is made commercially from brown seaweed extract. Over time, several research groups have formed various metal-polymer composites due to the immobilization of metal ions during the gelation process.
A pressure-fed circulation system operating in batch and continuous mode under full-band solar irradiation was studied to enhance solar hydrogen production from water using a novel 3D millisphere of photocatalyst encapsulated in an organic alginate hydrogel with high water retention capacity. The main emphasis was placed on the role of improving the adsorption of the water molecule on the active sites of the photocatalyst on the performance of solar hydrogen production.
From a functional point of view, the addition of sodium alginate increases the activity of the photocatalyst and its water retention capacity, thus enabling the process of continuous hydrogen generation. From an operational point of view, the presence of alginate increases the activity and water retention capacity of the photocatalyst, enabling the process of constant hydrogen generation.
Each spherical bead-shaped alginate-encapsulated photocatalyst functions as a miniature hydrogen producer or photocatalytic reactor. Alginate hydrogels have also shown exceptional recyclability and reuse. Their synthetic repeatability and linear scalability are confirmed by the fact that the total amount of hydrogen generated increases linearly with the number of beads encapsulated in the photocatalyst, while the volume normalized rate remains constant.
The degree of hydration – both pre-adsorption and dynamic adsorption of water – strongly influences the rate at which hydrogen is produced. A flow reactor is used to produce hydrogen at a constant flow rate; when the incoming flow rate falls below a critical value, the production rate remains constant, indicating that each spherical catalyst functions as a small hydrogen generator.
Professor Kargupta is experienced in transforming laboratory-scale prototypes into practical commercial applications, and our multidisciplinary team has expertise in solar hydrogen production, fuel cell electrolyte membrane/electrode fabrication and carbon sequestration. The team is trying to increase the capacity of hydrogen produced to power portable fuel cells in remote areas.
The main chemical used for photocatalyst encapsulation is sodium alginate, which is considered a food grade material (emulsifier, stabilizer, thickener and gelling agent) by the United States Food and Drug Administration and the European Commission. . The alginate hydrogel-based photocatalyst with an appropriate photoreactor will be assembled with high storage cells and fuel cells in the next two years. We plan to collaborate with industrial partners to develop this high-performance photocatalyst on an industrial scale.
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More information:
Sayantanu Mandal et al, rGO-CdS millispheres encapsulated in organic alginate for remarkable photocatalytic production of solar hydrogen, International Journal of Hydrogen Energy (2023). DOI: 10.1016/j.ijhydene.2023.09.137
Prof. Kajari Kargupta, Department of Chemical Engineering, Jadavpur University, received his Ph.D. on “Instability and Pattern Formation in Thin Films: Role of Heterogeneity, Evaporation and Sliding” in 1998 at IIT Kanpur. She has expertise in thin film systems, pattern generation, formation of nanostructures of different morphologies and their application. She has successfully completed several projects sponsored by SERB DST, UGC, DBT and DRDO and has to her credit over 100 publications in peer-reviewed journals. She has experience in formulating graphene-based bimetallic nano-hybrid materials of different morphologies and applying them as catalysts and electrocatalysts for hydrogen generation. In a previous DST-sponsored project, she explored the synthesis and characterization of graphene-based bimetallic nano-hybrid catalysts for hydrogen generation from sodium borohydride and borohydride electro-oxidation ; Based on composition-morphology-performance mapping, a novel core-shell connected G-Co-Pt nano-hybrid catalyst based on rGO that exhibits excellent electron transport property was explored for hydrogen generation as well as an ORR catalyst to reduce Pt loading. Dr. Kargupta has experience in the synthesis and characterization of electrocatalysts for electro-oxidation, oxygen reduction reaction and application of fuel cells. She explored photocatalytic and photoelectrocatalytic solar hydrogen production by water splitting; whose aim is to resolve key process bottlenecks and improve efficiency from solar to hydrogen. Based on experimental and quantum simulations, the role of nano-hybrid catalysts/photo-catalysts and photo-electro catalysts is analyzed and explored. Earlier, as part of the UGC major project, Prof. Kargupta explored different inorganic-organic nanocomposite membrane electrolytes as well as portable, durable and proton-conducting gel-like electrolytes, especially for portable battery application fuel. Prof. Kargupta has experience in managing 10 sponsored projects as PI and Co-PI. She also worked with NMRL, DRDO on a mission project related to fuel cell application as a research service provider.
Mr. Sayantanu Mandal is currently completing his Ph.D. in the Department of Chemical Engineering, Jadavpur University, under the supervision of Prof. Kajari Kargupta. For three years, he has been working on the generation of hydrogen and the manufacture of an electrolytic membrane for high-temperature fuel cells. Currently, he is also the Principal Investigator of a project under the Indian Science and Technology Engineering Facilities Map under the Government of India (I-STEM) with his guide Prof. Kajari Kargupta (I-STEM/Catalyticgrant/ acad_24/2022-23). He is also a permanent member of some of the prestigious global scientific organizations such as the International Association of Engineers (IAENG) and the International Academy of Science and Engineering for Development (IASED) Hong Kong. He is also part of the technical committee of the technical committee of MEAMT 2023, NanoMT 2023 and ICFMCE 2023 as a peer reviewer.
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