Plasma-synthetic photothermal materials may allow efficient solar-powered water purification

Technology for converting solar energy into thermal energy is constantly evolving and has many uses. Professor Ali El Khakani of the Institute National de La Recherche Scientifique (INRS)’s breakthrough in the lab has contributed significantly to this field.

Professor Elkakani specializes in plasma laser processes for the development of nanostructured materials. He and the team at the Energy Materia Telecomuna Center Research Center have developed a new photothermal material that converts sunlight into heat with unparalleled efficiency. The results of their study were published in the journal Scientific Reports.

For decades, stoichiometric titanium oxides have been known for their exceptional photocatalytic properties. The subsummation measurement form of this material, characterized by a slight deficiency of oxygen atoms, is called the “magneriphase” and exhibits properties of a particular composition.

Among these phases, Ti4O7 stands out as the variant that offers the most compelling electrical, chemical and catalytic properties. Although its photothermal behavior has been investigated in recent years, a groundbreaking study by Professor El Khakani’s team revealed the unparalleled potential of TI4O7 thin films for ultra-efficient photothermal conversion.

Pushing the limits of materials

One of the main constraints regarding the potential use of Ti4o7 was in the synthesis process and the final form of the resulting material.

“Traditionally, Ti4O7 has been synthesized in powder form using thermal reduction methods. This approach prevents the achievement of pure phase of the material, making it difficult to control its composition, morphology, and nanostructure,” says Ph.D. INRS Student and Publications Chief Author.

“These thermal reduction methods usually produce several chemical compositions and mixed phases. This limits access to the full potential of pure materials, particularly the electrical conductivity.” Furthermore, the generated powder is generally compressed into pellets, and the size of the resulting electrode is greatly limited to a few centimeters at most.

Professor El Khakani and his team turned to a technique known as magnetron sputtering (or RF magnetron plasma) and deposited a thin film of this material as a coating. This thin film deposition process is commonly used in the semiconductor industry.

“Ti4O7 coatings deposited via this method (a film with a thickness of several hundred nanometers) completely change the surface properties of the substrate. Otherwise, they vary in size or material compositions, from metal plates to silicon wafers or glass plates,” explains Professor Elkakani.

“Scientifically, the results of our research have made a significant contribution to establishing the fundamental relationship between the light absorbance capacity of Ti4O7 films and its light conversion efficiency for the first time,” adds Professor Elhakani.

Wide range of applications

By enabling controlled deposition of Ti4O7 films on a variety of substrates, INRS researchers have opened the door to many impactful applications. Ti4O7 coatings are poised to play an important role in the development of high-performance anodes for the decontamination of water containing persistent contaminants.

These highly corrosion-resistant conductive electrodes are also in high demand for electrochemical processes involved in the production of hydrogen and ammonia, two important economic sectors of Quebec. With its exceptional photothermal conversion capabilities, these coatings are also ideal for manufacturing smart heating windows, offering great benefits in terms of cost savings and energy efficiency.

“The ability to create thin photothermal coatings on reasonably sized surfaces, using only direct sunlight, retains the particular promise of passive desalination in niche applications that do not require external electrical energy input, unlike commonly used reverse osmosis processes,” concludes Professor Elkakani.